#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;
    }
    ll operator*(int i) const {
        return a + b * (ll)i;
    }
    int a, b;
};

ll dp[2048][2048];

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

    int n;
    cin >> n;

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

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

    dp[0][0] = 0;
    for (int i = 1; i <= n; i++) {
        dp[i][0] = 0;
        for (int j = 1; j < i; j++) {
            dp[i][j] = min(dp[i - 1][j], dp[i - 1][j - 1] + p[i - 1] * (j - 1));
        }
        dp[i][i] = dp[i - 1][i - 1] + p[i - 1] * (i - 1);
    }

    cout << dp[n][n - n / 3] << endl;

    return 0;
}