#include <algorithm>
#include <cassert>
#include <cctype>
#include <chrono>
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <vector>
using namespace std;

#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

const int INF = 0x3f3f3f3f, MOD = 1000000007;
const long long LINF = 0x3f3f3f3f3f3f3f3fLL;
/*-----------------------------------------*/
int main() {
  cin.tie(0); ios::sync_with_stdio(false);
  // freopen("input.txt", "r", stdin);

  int n; cin >> n;
  vector<pair<int, int> > ba(n); REP(i, n) cin >> ba[i].second >> ba[i].first;
  sort(ALL(ba), greater<pair<int, int> >());
  vector<vector<long long> > dp(n + 1, vector<long long>(n + 1, LINF));
  dp[0][0] = 0;
  FOR(i, 1, n + 1) REP(j, i + 1) {
    dp[i][j] = min((j > 0 ? dp[i - 1][j - 1] : LINF), dp[i - 1][j] + ba[i - 1].second + (long long)ba[i - 1].first * (i - j - 1));
  }
  cout << dp[n][n / 3] << '\n';
  return 0;
}