#include <queue>
#include <set>

class cyy {
public:
    int a;
    int b;

public:
    cyy(int i_a, int i_b) : a(i_a), b(i_b) {}
    bool operator<(const cyy &i_cyy) const { return (a + b) < (i_cyy.a + i_cyy.b); }
};

class csf {
public:
    int a;
    int b;

public:
    csf(int i_a, int i_b) : a(i_a), b(i_b) {}
    bool operator<(const csf &i_cyy) const {
        if (a < i_cyy.a)
            return true;
        else if (a > i_cyy.a)
            return false;
        else
            return b < i_cyy.b;
    }
};

class card {
public:
    int a;
    int b;
    card(int i_a, int i_b) : a(i_a), b(i_b) {}
    bool operator<(const card &i_cyy) const {
        if (a < i_cyy.a)
            return true;
        else if (a > i_cyy.a)
            return false;
        else
            return b < i_cyy.b;
    }
};

/*pq.push(2); cout<<pq.top()<<endl; pq.pop();*/

int main() {
    int num;
    int get_scores = 0;
    int a, b;
    set<card> search_tree;
    search_tree.clear();
    priority_queue<cyy, vector<cyy>> queue_cyy;
    priority_queue<csf, vector<csf>> queue_csf;
    cin >> num;
    for (int i = 0; i < num; i++) {
        cin >> a >> b;
        queue_cyy.push(cyy(a, b));
        queue_csf.push(csf(a, b));
    }
    for (int i = 0; i < num; i++) {
        if (i % 2 == 0) {
            csf tmp = queue_csf.top();
            queue_csf.pop();
            while (search_tree.find(card(tmp.a, tmp.b)) != search_tree.end()) {
                tmp = queue_csf.top();
                queue_csf.pop();
            }
        } else {
            cyy tmp = queue_cyy.top();
            queue_csf.pop();
            while (search_tree.find(card(tmp.a, tmp.b)) != search_tree.end()) {
                tmp = queue_cyy.top();
                queue_csf.pop();
            }
            get_scores += tmp.b;
        }
    }
    cout << get_scores;
    // cin.get();
    return 0;
}

/sandbox/1/a.cpp: In function 'int main()':
/sandbox/1/a.cpp:64:2: error: 'set' was not declared in this scope
  set<card> search_tree;
  ^~~
/sandbox/1/a.cpp:64:2: note: suggested alternative:
In file included from /usr/include/c++/8/set:61,
                 from /sandbox/1/a.cpp:2:
/usr/include/c++/8/bits/stl_set.h:94:11: note:   'std::set'
     class set
           ^~~
/sandbox/1/a.cpp:64:10: error: expected primary-expression before '>' token
  set<card> search_tree;
          ^
/sandbox/1/a.cpp:64:12: error: 'search_tree' was not declared in this scope
  set<card> search_tree;
            ^~~~~~~~~~~
/sandbox/1/a.cpp:66:2: error: 'priority_queue' was not declared in this scope
  priority_queue< cyy, vector<cyy>> queue_cyy;
  ^~~~~~~~~~~~~~
/sandbox/1/a.cpp:66:2: note: suggested alternative:
In file included from /usr/include/c++/8/queue:64,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/8/bits/stl_queue.h:423:11: note:   'std::priority_queue'
     class priority_queue
           ^~~~~~~~~~~~~~
/sandbox/1/a.cpp:66:21: error: expected primary-expression before ',' token
  priority_queue< cyy, vector<cyy>> queue_cyy;
                     ^
/sandbox/1/a.cpp:66:23: error: 'vector' was not declared in this scope
  priority_queue< cyy, vector<cyy>> queue_cyy;
                       ^~~~~~
/sandbox/1/a.cpp:66:23: note: suggested alternative:
In file included from /usr/include/c++/8/vector:64,
                 from /usr/include/c++/8/queue:61,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/8/bits/stl_vector.h:339:11: note:   'std::vector'
     class vector : protected _Vector_base<_Tp, _Alloc>
           ^~~~~~
/sandbox/1/a.cpp:66:33: error: expected primary-expression before '>>' token
  priority_queue< cyy, vector<cyy>> queue_cyy;
                                 ^~
/sandbox/1/a.cpp:66:36: error: 'queue_cyy' was not declared in this scope
  priority_queue< cyy, vector<cyy>> queue_cyy;
                                    ^~~~~~~~~
/sandbox/1/a.cpp:67:21: error: expected primary-expression before ',' token
  priority_queue< csf, vector<csf>> queue_csf;
                     ^
/sandbox/1/a.cpp:67:33: error: expected primary-expression before '>>' token
  priority_queue< csf, vector<csf>> queue_csf;
                                 ^~
/sandbox/1/a.cpp:67:36: error: 'queue_csf' was not declared in this scope
  priority_queue< csf, vector<csf>> queue_csf;
                                    ^~~~~~~~~
/sandbox/1/a.cpp:68:2: error: 'cin' was not declared in this scope
  cin >> num;
  ^~~
/sandbox/1/a.cpp:68:2: note: suggested alternative: 'main'
  cin >> num;
  ^~~
  main
/sandbox/1/a.cpp:99:2: error: 'cout' was not declared in this scope
  cout << get_scores;
  ^~~~