#include <algorithm>
#include <iostream>
#include <vector>

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

void chmin(int64_t &l, int64_t r) {
  if (l > r) l = r;
}

int main() {

  int n;
  cin >> n;
  struct Item {
    int64_t a, b;
  };
  vector<Item> its(n);
  rep(i, n) cin >> its[i].a >> its[i].b;

  sort(its.begin(), its.end(),
       [&](const Item &l, const Item &r) { return l.b > r.b; });
  vector<vector<int64_t>> dp(n + 1, vector<int64_t>(n + 1, 1e18));
  dp[0][0] = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j <= i; j++) {
      if (j >= 1) chmin(dp[i][j], dp[i - 1][j - 1]);
      if (i - 1 >= j) {
        chmin(dp[i][j],
              dp[i - 1][j] + (its[i - 1].a + its[i - 1].b * (i - j - 1)));
      }
    }
  }

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

  return 0;
}