#include <bits/stdc++.h>
using namespace std;
class Visitor {
public:
    double ai;
    double bi;
    double pri;

public:
    bool operator<(Visitor b) { return this->pri < b.pri; }
    bool operator>(Visitor b) { return this->pri > b.pri; }
    void print() { printf("ai=%f bi=%f priorityi=%f\n", ai, bi, pri); }
};
int main() {
    int n = 0;
    cin >> n;
    cin.ignore(100, '\n');
    list<Visitor> arr;
    // Visitor test;
    // cin>>test.ai>>test.bi;
    // test.pri=test.bi/test.ai;
    // test.print();
    for (int i = 0; i < n; i++) {
        Visitor test;
        cin >> test.ai >> test.bi;
        cin.ignore(100, '\n');
        test.pri = test.bi / test.ai;
        //	test.print();
        arr.push_back(test);
    }
    arr.sort();
    list<Visitor>::iterator vi;
    long long sum = 0, time = 0;
    for (vi = arr.begin(); vi != arr.end(); vi++) {
        //	vi->print();
        time += (long long)vi->bi;
        sum += (time * vi->ai);
    }
    // cout<<endl;
    cout << sum;
    return 0;
}