#include <iostream>
#include <utility>
#include <algorithm>
#define llint long long

using namespace std;

llint n;
pair<llint, llint> p[2005];
llint dp[2005][2005];

int main(void)
{
	cin >> n;
	for(int i = 1; i <= n; i++) cin >> p[i].second >> p[i].first;
	sort(p+1, p+n+1);
	reverse(p+1, p+n+1);
	
	
	for(int i = 0; i <= n; i++){
		for(int j = 0; j <= n; j++){
			dp[i][j] = 1e18;
		}
	}
	dp[0][0] = 0;
	
	for(int i = 0; i < n; i++){
		for(int j = 0; j <= n; j++){
			dp[i+1][j] = min(dp[i+1][j], dp[i][j]);
			if(j+1 <= n) dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j] + p[i+1].first*j + p[i+1].second);
		}
	}
	cout << dp[n][n-n/3] << endl;
	
	return 0;
}