#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;
using ll = long long;

const ll INF = 1LL << 50;

template <class T>
vector<T> Vec(size_t l, T v) { return vector<T>(l, v); }

template <class T, class... Ts>
auto Vec(size_t l, Ts... ts) {
    return vector<decltype(Vec<T>(ts...))>(l, Vec<T>(ts...));
}

int main() {
    int N;
    cin >> N;
    int day = N - N / 3;

    vector<pair<ll, ll>> A(N);
    for (auto& p : A) {
        cin >> p.second >> p.first;
    }
    sort(A.rbegin(), A.rend());

    auto dp = Vec<ll>(N + 1, day + 1, INF);
    dp[0][0] = 0;
    for (int i = 1; i <= N; ++i) {
        dp[i][0] = 0;
        auto p = A[i - 1];
        for (int d = 1; d <= day; ++d) {
            dp[i][d] = min(dp[i - 1][d], dp[i - 1][d - 1] + p.second + p.first * (d - 1));
        }
    }

    cout << dp[N][day] << endl;
    return 0;
}