#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll INF = 1e18;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<ll> a(n), b(n);
    vector<int> idxs;
    for (int i = 0; i < n; i++) {
        idxs.push_back(i);
        cin >> a[i] >> b[i];
    }

    sort(idxs.begin(), idxs.end(), [&](const int i1, const int i2){return b[i1] > b[i2];});

    int x = n / 3;
    vector<ll> dp(x + 1, INF);
    dp[0] = 0;
    for (int i = 0; i < n; i++) {
        int ii = idxs[i];
        for (int j = min(x, i); j >= 0; j--) {
            if (j < x) dp[j + 1] = min(dp[j + 1], dp[j]);
            dp[j] += a[ii] + b[ii] * (i - j);
        }
    }
    cout << dp[x] << endl;

    return 0;
}