#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <vector>
#include <stack>
#include <set>
#include <cmath>
#include <bitset>
#define lson node << 1
#define rson node << 1 | 1
using namespace std;
#define ll long long
const ll maxn = 5e5 + 10;
ll read() {
    char c = getchar();
    ll x = 0;
    ll flag = 1;
    while (c < '0' || c > '9') {
        if (c == '-')
            flag = -1;
        c = getchar();
    }
    while (c >= '0' && c <= '9') {
        x = x * 10 + c - 48;
        c = getchar();
    }
    x *= flag;
    return x;
}
struct node {
    int x, y;
} a[maxn];
int cmp(node a, node b) { return a.y * b.x < a.x * b.y; }
int n;
int main() {
    n = read();
    for (int i = 1; i <= n; i++) {
        a[i].x = read(), a[i].y = read();
    }
    sort(a + 1, a + n + 1, cmp);
    ll ans = 0, ti = 0;
    for (int i = 1; i <= n; i++) {
        ti += a[i].y;
        ans += a[i].x * ti;
    }
    printf("%lld", ans);
    return 0;
}