#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

long long cost[2001][2001];

int main () {
    int n; cin >> n;
    vector<pair<int, int> > P(n);
    for (auto &p : P) cin >> p.second >> p.first;
    sort(P.rbegin(), P.rend());

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            long long c = cost[i-1][j-1] + P[i-1].second + P[i-1].first * (j-1);
            if (i == j || cost[i-1][j] > c) {
                cost[i][j] = c;
            } else {
                cost[i][j] = cost[i-1][j];
            }
        }
    }
    cout << cost[n][2*(n+1)/3] << endl;
}