#include <iostream>
#include <string>
#include <cstring>
#include <ctime>
#include <cmath>
#include <fstream>
#include <cstdlib>
using namespace std;
long long min(pai ar[], char a, int b);
struct pai {
    long long ana;
    long long bna;
    char naderen;
};
int main() {
    long a;
    cin >> a;
    pai* paizongliang = new pai[a];
    long long i = 0, k = 0;
    while (i < a) {
        cin >> paizongliang[i].ana >> paizongliang[i].bna;
        i++;
    }
    for (i = 0; i < a; i++) paizongliang[i].naderen = 'none';
    for (i = 0; i < a; i++) {
        for (long long j = i; j < a; j++) {
            pai zhongjian;
            if (paizongliang[i] < paizongliang[j]) {
                zhongjian = paizongliang[i];
                paizongliang[i] = paizongliang[j];
                paizongliang[j] = zhongjian;
            }
        }
    }
    i = 0;
    while (i < a) {
        if (i < a) {
            paizongliang[i].naderen = 'a';
                        if (paizongliang[i].bna > min1(paizongliang, 'b', a)
			{
                paizongliang[i].naderen = 'b';
                paizongliang[min2(paizonglaing, 'b', a)].naderen = 'a';
			}
			i++;
        }
        if (i < a) {
            paizongliang[i].naderen = 'b';
            i++;
        }
    }
    for (i = 0; i < a; i++) {
        if (paizongliang[i].naderen == 'b')
            k = k + paizongliang[i].ana;
    }
    cout << k;
    return 0;
}
long long min1(pai ar[], char a, int b) {
    long long i = 0;
    long long j = 0;
    long long k[b] = { 0 };
    for (i; i < b; i++) {
        if (ar[i].naderen == a) {
            k[j] = i;
            j++;
        }
    }
    i = j = 0;
    for (j; j < b; j++) {
        if (ar[k[j]].bna < ar[k[i]].bna)
            i = j;
    }
    return ar[k[i]].bna;
}
long long min2(pai ar[], char a, int b) {
    long long i = 0;
    long long j = 0;
    long long k[b] = { 0 };
    for (i; i < b; i++) {
        if (ar[i].naderen == a) {
            k[j] = i;
            j++;
        }
    }
    i = j = 0;
    for (j; j < b; j++) {
        if (ar[k[j]].bna < ar[k[i]].bna)
            i = j;
    }
    return k[i];
}

/sandbox/1/a.cpp:28:29: warning: multi-character character constant [-Wmultichar]
   paizongliang[i].naderen = 'none';
                             ^
/sandbox/1/a.cpp:9:15: error: 'pai' was not declared in this scope
 long long min(pai ar[], char a,int b);
               ^
/sandbox/1/a.cpp:9:25: error: expected primary-expression before 'char'
 long long min(pai ar[], char a,int b);
                         ^
/sandbox/1/a.cpp:9:32: error: expected primary-expression before 'int'
 long long min(pai ar[], char a,int b);
                                ^
/sandbox/1/a.cpp:9:37: error: expression list treated as compound expression in initializer [-fpermissive]
 long long min(pai ar[], char a,int b);
                                     ^
/sandbox/1/a.cpp: In function 'int main()':
/sandbox/1/a.cpp:28:27: warning: overflow in implicit constant conversion [-Woverflow]
   paizongliang[i].naderen = 'none';
                           ^
/sandbox/1/a.cpp:34:24: error: no match for 'operator<' (operand types are 'pai' and 'pai')
    if (paizongliang[i] < paizongliang[j])
                        ^
/sandbox/1/a.cpp:34:24: note: candidates are:
In file included from /opt/noilinux/usr/include/c++/4.8/bits/stl_algobase.h:64:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/char_traits.h:39,
                 from /opt/noilinux/usr/include/c++/4.8/ios:40,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/stl_pair.h:220:5: note: template<class _T1, class _T2> constexpr bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
     ^
/opt/noilinux/usr/include/c++/4.8/bits/stl_pair.h:220:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::pair<_T1, _T2>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/bits/stl_algobase.h:67:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/char_traits.h:39,
                 from /opt/noilinux/usr/include/c++/4.8/ios:40,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:297:5: note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
     operator<(const reverse_iterator<_Iterator>& __x,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:297:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::reverse_iterator<_Iterator>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/bits/stl_algobase.h:67:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/char_traits.h:39,
                 from /opt/noilinux/usr/include/c++/4.8/ios:40,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:347:5: note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)
     operator<(const reverse_iterator<_IteratorL>& __x,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:347:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::reverse_iterator<_Iterator>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/bits/stl_algobase.h:67:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/char_traits.h:39,
                 from /opt/noilinux/usr/include/c++/4.8/ios:40,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:1055:5: note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_IteratorR>&)
     operator<(const move_iterator<_IteratorL>& __x,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:1055:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::move_iterator<_Iterator>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/bits/stl_algobase.h:67:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/char_traits.h:39,
                 from /opt/noilinux/usr/include/c++/4.8/ios:40,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:1061:5: note: template<class _Iterator> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_Iterator>&)
     operator<(const move_iterator<_Iterator>& __x,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/stl_iterator.h:1061:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::move_iterator<_Iterator>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/string:52:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/locale_classes.h:40,
                 from /opt/noilinux/usr/include/c++/4.8/bits/ios_base.h:41,
                 from /opt/noilinux/usr/include/c++/4.8/ios:42,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2569:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2569:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::basic_string<_CharT, _Traits, _Alloc>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/string:52:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/locale_classes.h:40,
                 from /opt/noilinux/usr/include/c++/4.8/bits/ios_base.h:41,
                 from /opt/noilinux/usr/include/c++/4.8/ios:42,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2581:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2581:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   'pai' is not derived from 'const std::basic_string<_CharT, _Traits, _Alloc>'
    if (paizongliang[i] < paizongliang[j])
                                        ^
In file included from /opt/noilinux/usr/include/c++/4.8/string:52:0,
                 from /opt/noilinux/usr/include/c++/4.8/bits/locale_classes.h:40,
                 from /opt/noilinux/usr/include/c++/4.8/bits/ios_base.h:41,
                 from /opt/noilinux/usr/include/c++/4.8/ios:42,
                 from /opt/noilinux/usr/include/c++/4.8/ostream:38,
                 from /opt/noilinux/usr/include/c++/4.8/iostream:39,
                 from /sandbox/1/a.cpp:1:
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2593:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
     operator<(const _CharT* __lhs,
     ^
/opt/noilinux/usr/include/c++/4.8/bits/basic_string.h:2593:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:34:40: note:   mismatched types 'const _CharT*' and 'pai'
    if (paizongliang[i] < paizongliang[j])
                                        ^
/sandbox/1/a.cpp:48:55: error: 'min1' was not declared in this scope
    if (paizongliang[i].bna > min1(paizongliang, 'b', a)
                                                       ^
/sandbox/1/a.cpp:49:4: error: expected ')' before '{' token
    {
    ^
/sandbox/1/a.cpp: In function 'long long int min1(pai*, char, int)':
/sandbox/1/a.cpp:73:22: error: variable-sized object 'k' may not be initialized
   long long k[b] = {0};
                      ^
/sandbox/1/a.cpp: In function 'long long int min2(pai*, char, int)':
/sandbox/1/a.cpp:94:24: error: variable-sized object 'k' may not be initialized
   long long k[b] = { 0 };
                        ^