#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

struct P {
    bool operator<(const P& p) const {
        return b > p.b;
    }
    int a, b;
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;

    int m = n - n / 3;

    vector<P> p(n);
    for (int i = 0; i < n; i++) {
        cin >> p[i].a >> p[i].b;
    }

    sort(p.begin(), p.end());

    ll dp[2001];
    dp[0] = 0;
    for (int j = 1; j <= n; j++) {
        dp[j] = 1LL << 60;
    }
    for (int i = 1; i <= n; i++) {
        for (int j = min(i, m); j > 0; j--) {
            dp[j] = min(dp[j], dp[j - 1] + p[i - 1].a + p[i - 1].b * (ll)(j - 1));
        }
    }

    cout << dp[m] << endl;

    return 0;
}