#include <iostream>
using namespace std;
int main() {
    float a[100001];
    float b[100001];
    float c[100001];
    int k;
    cin >> k;
    int i;
    int j = 0;
    int d = 0;
    for (i = 0; i < k; i++) {
        cin >> a[i] >> b[i];
    }
    long sum = 0;
    for (j = 0; j < k; j++) {
        for (i = j; i < k; i++) {
            c[i] = a[i] / b[i];
        }
        float cmax = c[j];
        float bmax = b[j];
        float amax = a[j];
        int t1 = j;
        int flag = 0;
        for (i = j + 1; i < k; i++) {
            if (c[i] > cmax) {
                t1 = i;
                cmax = c[i];
                bmax = b[i];
                amax = a[i];
                flag = 1;
            }
        }
        if (flag == 1) {
            b[t1] = b[j];
            b[j] = bmax;
            a[t1] = a[j];
            a[j] = amax;
            c[t1] = c[j];
            c[j] = cmax;
        }
        d = bmax + d;
        sum = sum + amax * d;
    }
    cout << sum;
}