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

void solve() {
    int n, s;
    std::cin >> n >> s;

    int psum = 0;
    std::vector<std::pair<int, int>> ps;
    {
        std::vector<int> xs(n), ys(n);
        for (auto& x : xs) std::cin >> x;
        for (auto& y : ys) std::cin >> y;

        for (int i = 0; i < n; ++i) {
            int d = xs[i] - s;
            if (d >= 0) {
                psum += d;
            } else {
                ps.emplace_back(-d, ys[i]);
            }
        }
    }

    if ((int)ps.size() == n) {
        std::cout << -1 << "\n";
        return;
    }

    std::vector<int> dp(psum + 1, 0);
    for (auto [d, c] : ps) {
        for (int i = psum; i >= 0; --i) {
            dp[i] += c;
            if (i >= d) dp[i] = std::min(dp[i], dp[i - d]);
        }
    }

    std::cout << dp[psum] << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}