#include <bits/stdc++.h>
using namespace std;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

int main() {
    constexpr int inf = INT_MAX / 4;

    int n, x; cin >> n >> x;
    auto a = vec<int>(uns, n);
    auto b = vec<int>(uns, n);
    for (auto &e : a) cin >> e;
    for (auto &e : b) cin >> e;

    for (auto &e : a) {
        e -= x;
        e *= -1;
    }

    if (0 < *min_element(begin(a), end(a))) {
        cout << -1 << endl;
        return 0;
    }

    int all = accumulate(begin(a), end(a), 0);
    if (all <= 0) {
        cout << 0 << endl;
        return 0;
    }

    auto dp = vec<int>(inf, n + 1, all + 1);
    dp[0][0] = 0;

    for (int i = 1; i <= n; ++i) {
        for (int j = 0; j <= all; ++j) {
            if (a[i - 1] <= 0) {
                dp[i][j] = dp[i - 1][j];
            }
            else {
                dp[i][j] = min(dp[i - 1][j], dp[i - 1][max(0, j - a[i - 1])] + b[i - 1]);
            }
        }
    }

    cout << dp[n][all] << endl;
}