#include <bits/stdc++.h>
using namespace std;
int main() {
    int n; cin >> n;
    vector<pair<long long, long long>> v;
    for (int i = 0; i < n; i++) {
        long long a, b; cin >> a >> b;
        v.emplace_back(b, a);
    }
    sort(v.rbegin(), v.rend());
    vector<vector<long long>> dp(n+1, vector<long long>(n+1, 1e12));
    dp[0][0] = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++) {
            // dp[i][j]
            dp[i+1][j] = min(dp[i+1][j], dp[i][j]+v[i].second+v[i].first*(i-j));
            dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j]);
        }
    }
    cout << dp[n][n/3] << endl;
    return 0;
}