#include <stdio.h>
#include <stdlib.h>

int cmp (const void *a, const void *b) {
  long long *a_ = (long long *)a;
  long long *b_ = (long long *)b;
  
  if (b_[0]*a_[1] < a_[0]*b_[1]) {
    return 1;
  }
  
  if (b_[0]*a_[1] > a_[0]*b_[1]) {
    return -1;
  }
  
  return 0;
}

int main () {
  int n = 0;
  long long ab[200000][2] = {};
  
  int res = 0;
  
  long long ans = 0LL;
  long long sum = 0LL;
  
  res = scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    res = scanf("%lld", ab[i]);
    res = scanf("%lld", ab[i]+1);
  }
  
  qsort(ab, n, sizeof(long long)*2, cmp);
  
  for (int i = 0; i < n; i++) {
    ans += ab[i][0]*sum;
    sum += ab[i][1];
  }
  
  printf("%lld\n", ans);
  return 0;
}