#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

struct ST {
  ll val;
  ll A, B;
  int i;
};
bool operator<(const ST& a, const ST& b){
  if(a.val == b.val) return a.B < b.B;
  return a.val > b.val;
}

priority_queue<ST> que[2005];
bool checked[2005];

int main(){
  int N;
  cin >> N;

  int M = 0;
  {
    vector<int> tmp(N,0);
    int j = N-1;
    rep(d,N){
      if(tmp[d] == -1) break;
      M++;
      if(d%2 == 1){
        tmp[j] = -1;
        j--;
      }
    }
  }

  vector<ST> v;
  rep(i,N){
    ll a, b;
    cin >> a >> b;
    v.push_back((ST){0LL,a,b,i});
  }

  rep(i,N-M){
    ll d = M+i;
    vector<ST> w;
    rep(j,v.size()){
      ST tmp = v[j];
      tmp.val = tmp.A + d * tmp.B;
      w.push_back(tmp);
    }
    sort(ALLOF(w));
    rep(j,w.size()){
      if(checked[w[j].i]) continue;
      checked[w[j].i] = true;
      break;
    }
  }

  ll ret = 0;
  vector<ll> bs;
  rep(i,N){
    if(checked[i]) continue;
    bs.push_back(v[i].B);
    ret += v[i].A;
  }
  sort(ALLOF(bs));
  reverse(ALLOF(bs));
  rep(i,bs.size()){
    ret += i * bs[i];
  }

  cout << ret << endl;
  return 0;
}