#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
using namespace std;
int n;
long long ans, t = 0;
struct node {
    long long a, b;
};
node s[100010];
bool cmp(node A, node B) { return A.a * B.b > A.b * B.a; }
int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        scanf("%lld%lld", &s[i].a, &s[i].b);
    }
    sort(s + 1, s + n + 1, cmp);
    for (int i = 1; i <= n; i++) {
        t += s[i].b;
        ans += t * s[i].a;
    }
    printf("%lld\n", ans);
    system("pause");
    return 0;
}

/sandbox/1/a.c:3:9: fatal error: 'algorithm' file not found
#include<algorithm>
        ^~~~~~~~~~~
1 error generated.