#include <iostream>

 #include <stdio.h>

 #include <algorithm>

 #define ll long long

 using namespace std;

 const int MAXN = 1e4+;

 pair<ll, ll> p[MAXN];

 int main(void){

     int n;

     ll ans=, sum=;

     scanf("%d", &n);

     for(int i=; i<n; i++){

         scanf("%lld%lld", &p[i].first, &p[i].second);

         ans+=p[i].second;

     }

     ans>>=;

     sort(p, p+n);

     ll cnt=;

     int indx=-;

     while(){

         cnt += p[++indx].second;

         if(cnt >= ans) break;

     }

     for(int i=; i<n; i++){

         if(i == indx) continue;

         sum += abs(p[indx].first-p[i].first)*p[i].second;

     }

     printf("%lld\n", sum);

     return ;

 }