#include <iostream>
using namespace std;
int main(){
    int n;  cin >> n;
    int res = 0;
    for(int i = 0; i < n; i ++ ){
        int a, b;   cin >> a >> b;
        res += a * b;
    }
    if(res <= 0)    cout << 0 << endl;
    else    cout << res << endl;
    return 0;
}