#include "bits/stdc++.h"

using namespace std;

void solve(void)
{
	int n;
	cin >> n;
	vector<pair<long, long>> ps(n);
	for (auto& p : ps)
	{
		cin >> p.second >> p.first;
	}
	sort(ps.rbegin(), ps.rend());
	vector<long> dp(n+1, 1L<<30);
	dp[0] = 0;
	for (const auto &p : ps)
	{
		vector<long> nx(dp);
		for (int i = 0; i < n; i++)
		{
			nx[i+1] = min(nx[i+1], dp[i] + p.first * i + p.second);
		}
		swap(dp, nx);
	}
	cout << dp[n-n/3] << endl;
}

int main()
{
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}