#include <bits/stdc++.h>
using namespace std::literals::string_literals;
using i64 = long long;
using std::cout;
using std::endl;
using std::cin;

int main() {
	int n; scanf("%d", &n); std::vector<int> a(n), b(n);
	std::vector<std::pair<int, int>> vec;
	for(int i = 0; i < n; i++) {
		scanf("%d%d", &a[i], &b[i]);
		
		vec.push_back({b[i], a[i]});
	}
	sort(begin(vec), end(vec)); reverse(begin(vec), end(vec));
	
	int C = 0;
	for(int i = 0, count = n; i < n and count > 0; i++) {
		count--; C++;
		if(i % 2) count--;
	}
	
	std::vector<std::vector<i64>> dp(n + 1, std::vector<i64>(C + 1, 1LL << 60)); dp[0][0] = 0;
	for(int i = 0; i < n; i++) {
		for(int j = 0; j <= C; j++) dp[i + 1][j] = dp[i][j];
		for(int j = 0; j < C; j++) {
			i64 A = vec[i].second, B = vec[i].first;
	
			dp[i + 1][j + 1] = std::min(dp[i + 1][j + 1], dp[i][j] + (A + B * (i64)j));
		}
	}
	printf("%lld\n", dp[n][C]);
	return 0;
}