#include<iostream>
#include<vector>
#include<algorithm>
#include<numeric>
using namespace std;

#define rep(i,n) for(int i=0;i<(n);i++)

int main(){

  int n; cin>> n;
  vector<int> a(n), b(n);
  rep(i, n) cin>> a[i]>> b[i];

  vector<int> perm(n);
  iota(perm.begin(), perm.end(), 0);
  int mn=1e9;
  do{
    int sum=0;
    for(int j=0, _i=0; _i<n; j++){
      auto i=perm[_i];
      sum+=a[i]+b[i]*j;
      _i++;
      if(j%2==1) _i++;  
    }
    mn=min(mn, sum);
  }while(next_permutation(perm.begin(), perm.end()));

  cout<< mn<< endl;
  return 0;
}