#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll N, S=0, ans=0;
    cin >> N;
    vector<ll> A(N+1), B(N+1), sa(N+2), sb(N+2);
    for (int i=1; i<=N; i++) cin >> A[i] >> B[i];
    for (int i=N; i>=1; i--){
        sa[i] = sa[i+1] + A[i];
        sb[i] = sb[i+1] + B[i];
    }

    for (int i=1; i<=N; i++){
        if (A[i] * sb[i+1] >= B[i] * sa[i+1]){
            ans += A[i] * (sb[i+1] + S);
        }
        else{
            ans += S * A[i];
            S += B[i];
        }
    }

    cout << ans << endl;

    return 0;
}