#include <bits/stdc++.h>
using namespace std;
long long int dp[2010][2010];
long long int a[2010];
long long int b[2010];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i] >> b[i];
  }
  for (int i = 0; i <= 2000; i++) {
    for (int j = 0; j <= 2000; j++) {
      dp[i][j] = 10000000000000000;
    }
  }
  dp[0][0] = 0;
  for (int i = 1; i <= n; i++) {
    long long int o = a[i] + 1;
    for (int j = 0; j <= n; j++) {
      o = a[i] + 1;
      if (j == 0) {
        dp[i][j] = 0;
      }
      if (o >= j) {
        o = j;
      }
      if (j >= o) {
        dp[i][j] = min(b[i] + dp[i - 1][j - (o)], dp[i][j]);
      }
      dp[i][j] = min(dp[i][j], dp[i - 1][j]);
    }
  }
  cout << dp[n][n] << endl;
}
