/* -*- coding: utf-8 -*-
 *
 * 2284.cc:  No.2284 Assembly - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], bs[MAX_N];
ll ass[MAX_N + 1], bss[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d%d", as + i, bs + i);

  for (int i = 0; i < n; i++)
    ass[i + 1] = ass[i] + as[i], bss[i + 1] = bss[i] + bs[i];

  ll sum = 0, fb = 0, ta = 0;
  for (int i = 0; i < n; i++) {
    sum += fb * as[i] + ta * bs[i];
    if ((ass[n] - ass[i]) * bs[i] >= (bss[n] - bss[i]) * as[i])
      fb += bs[i];
    else
      ta += as[i];
  }

  printf("%lld\n", sum);
  
  return 0;
}