#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
  dp[i][j]
    iコメの商品まででjこ購入
}*/

signed main()
{
  int n;
  cin >> n;

  vi a(n), b(n);
  rep(i, n){
    cin >> a[i] >> b[i];
  }

  vector<pii> v;
  rep(i, n) v.pb({b[i], a[i]});
  sort(all(v)); reverse(all(v));

  vvi dp(n+1, vi(n+1, inf));
  dp[0][0] = 0;
  rep(i, n){
    rep(j, n){
      dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j]+v[i].second+v[i].first*j);
      dp[i+1][j] = min(dp[i+1][j], dp[i][j]);
    }
  }

  cout << dp[n][n-n/3] << endl;

  return 0;
}