#include <bits/stdc++.h>

#define rep(i, a, b) for(int i = (a); i <= (b); i ++)
using std::cin, std::cout, std::cerr;
using ll = long long;

void Solve() {
    int n; cin >> n;
    std::vector<std::pair<int, int>> ab(n);
    rep(i, 0, n - 1) {
        int a, b; cin >> a >> b;
        ab[i] = {a, b};
    }
    std::sort(ab.begin(), ab.end(), [](auto l, auto r) {
        return l.second > r.second;
    });

    std::vector f(n + 1, std::vector<ll>(n + 1, 1e18L));
    f[0][0] = 0;

    rep(i, 1, n) rep(j, 0, i) {
        auto [a, b] = ab[i - 1];
        f[i][j] = std::min(f[i][j], f[i - 1][j]);
        if(j > 0)
            f[i][j] = std::min(f[i][j], f[i - 1][j - 1] + ll(j - 1) * b + a);
    }

    int m = n - n / 3;
    cout << f[n][m] << '\n';
}

int main() {
    std::ios::sync_with_stdio(false);
    int T = 1;
    while(T --) {
        Solve();
    }
}