#include <iostream>
#include <algorithm>
#include <cstring>
#include <sstream>
#include <map>
#include <queue>
#include <set>
#include <vector>
#include <stack>
#include <cstdio>
#include <cmath>
#include <bitset>
#define mk make_pair
#define pb push_back
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> pos;

const ll MOD = 1234567, N = 2010, dx[4] = { -1,1,0,0 }, dy[4] = { 0,0,-1,1 }, MIN = -72340172838, MAX = 72340172838;

ll mn(ll a, ll b) {
	if (a == -1)return b;
	if (b == -1)return a;
	return min(a, b);
}
static ll gcd(ll v1, ll v2) {
	if (v1 == 0)return v2; if (v2 == 0)return v1; if (v2 > v1)return gcd(v2%v1, v1); return gcd(v1%v2, v2);
}

ll pw(ll v1, ll v2) {
	ll v3 = 1;
	while (v2 > 0) {
		if (v2 % 2)v3 = (v3*v1) % MOD;
		v1 = (v1*v1) % MOD;
		v2 /= 2;
	}
	return v3;
}

ll n,dp[N][N],n2;
pos g[N];
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) { cin >> g[i].second >> g[i].first; g[i].first *= -1; }
	sort(g + 1, g + n + 1);
	n2 = n - (n / 3);
	memset(dp, -1, sizeof(dp));
	dp[1][0] = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = 0; j <= n2; j++) {
			dp[i + 1][j] = mn(dp[i + 1][j], dp[i][j]);
			if (j + 1 <= n2 && dp[i][j] != -1)dp[i + 1][j + 1] = mn(dp[i + 1][j + 1], dp[i][j] + g[i].second - g[i].first*j);
		}
	}
	cout << dp[n + 1][n2] << endl;
	return 0;
}

/*
static int x;
void InitA(int T, int X) { x = X; }
int GameA(int I, int J) { 
	gcd(1, 2);
	if (I - 1 >= 1)return -1;
	if (I + 1 <= 4)return -2;
	if (J - 1 >= 1)return -3;
	if (J + 1 <= 4)return -4;
}
void InitB(int T) { return; }
int GameB(int I, int J) {
	gcd(1, 2);
	return x;
	if (I - 1 >= 1)return -1;
	if (I + 1 <= 4)return -2; 
	if (J - 1 >= 1)return -3; 
	if (J + 1 <= 4)return -4;
}
*/