#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 200003
#define MOD 1000000007
#define INF 1000000000000000000

int main(){
  int N;
  cin>>N;
  vector<pair<ll,ll>> BA(N);
  for(int i=0;i<N;i++){
    cin>>BA[i].second>>BA[i].first;
  }
  sort(BA.begin(),BA.end());
  reverse(BA.begin(),BA.end());

  int n;
  if(N%3==0){
    n=N*2/3;
  }else if(N%3==1){
    n=(N-1)*2/3+1;
  }else{
    n=(N+1)*2/3;
  }

  vector<vector<ll>> dp(N+1,vector<ll>(n+1,INF));
  dp[0][0]=0;
  for(int i=0;i<N;i++){
    ll A=BA[i].second;
    ll B=BA[i].first;
    for(int j=0;j<=n;j++){
      dp[i+1][j]=dp[i][j];
    }
    for(int j=0;j<n;j++){
      dp[i+1][j+1]=min<ll>(dp[i+1][j+1],dp[i][j]+A+B*(ll)j);
    }
  }

  cout<<dp[N][n]<<endl;
}