/* -*- coding: utf-8 -*-
 *
 * 798.cc:  No.798 コレクション - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100;
const int MAX_M = MAX_N / 3;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;
typedef pair<int,int> pii;

/* global variables */

pii bas[MAX_N];
ll dp[MAX_N + 1][MAX_M + 1];

/* subroutines */

inline void setmin(ll &a, ll b) { if (a > b) a = b; }

/* main */

int main() {
  int n;
  scanf("%d", &n);

  for (int i = 0; i < n; i++)
    scanf("%d%d", &bas[i].second, &bas[i].first);
  sort(bas, bas + n, greater<pii>());

  int m = n / 3;
  for (int i = 0; i <= n; i++)
    fill(dp[i], dp[i] + m + 1, LINF);
  dp[0][0] = 0;

  for (int i = 0; i < n; i++) {
    int &ai = bas[i].second, &bi = bas[i].first;
    for (int j = 0; j <= i && j <= m; j++)
      if (dp[i][j] < LINF) {
	if (j < m) setmin(dp[i + 1][j + 1], dp[i][j]);
	setmin(dp[i + 1][j], dp[i][j] + ai + bi * (i - j));
      }
  }

  printf("%lld\n", dp[n][m]);
  return 0;
}