#include <iostream>
using namespace std;
long summin(int j, long sum, float a[], float b[], float c[], int k, int d);
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;
    cout << summin(j, sum, a, b, c, k, d) << endl;
}
long summin(int j, long sum, float a[], float b[], float c[], int k, int d) {
    int i;
    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;
    j = j + 1;
    if (j == k)
        return sum;
    else
        summin(j, sum, a, b, c, k, d);
}