#include<iostream>
#include<vector>
#include<climits>

typedef long long ll;

int main(int argc, char const *argv[]) {
    ll n;
    std::cin >> n;
    std::vector<ll> a(n), b(n);
    for (ll i = 0; i < n; i++) std::cin >> a[i] >> b[i];

    std::vector<std::vector<ll>> dp(n + 1, std::vector<ll>(1 << n, LLONG_MAX));
    dp[0][0] = 0;
    for (ll x = 0; x < n; x++) {
        for (ll y = 0; y < (1 << n); y++) {
            if (dp[x][y] == LLONG_MAX) continue;

            for (ll z = 0; z < n; z++) {
                if ((y & (1 << z)) != 0) continue;
                dp[x + 1][y | (1 << z)] = std::min(dp[x + 1][y | (1 << z)], dp[x][y] + a[z] + b[z] * x);
            }

            if (x % 2 != 0) {
                for (ll s = 0; s < n; s++) {
                    for (ll t = s + 1; t < n; t++) {
                        if ((y & (1 << s)) != 0 || (y & (1 << t)) != 0) continue;
                        ll u = std::min(a[s] + b[s] * x, a[t] + b[t] * x);
                        dp[x + 1][y | (1 << s) | (1 << t)] = std::min(dp[x + 1][y | (1 << s) | (1 << t)], dp[x][y] + u);
                    }
                }
            }
        }
    }

    ll ans = LLONG_MAX;
    for (ll i = 0; i <= n; i++) {
        ans = std::min(ans, dp[i][(1 << n) - 1]);
    }

    std::cout << ans << std::endl;
}