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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll N, X;
    cin >> N >> X;
    vector<ll> A(N), B(N);
    for(auto &v: A)cin >> v;
    for(auto &v: B)cin >> v;
    ll s = accumulate(B.begin(), B.end(), 0ll);
    vector<vector<ll>> dp(N + 1, vector<ll>(100 * N + 1, -(1ll << 60)));
    dp[0][0] = 0;
    for(int i = 0; i < N; i++){
        for(int j = i; j >= 0; j--){
            for(int k = j * 100; k >= 0; k--){
                dp[j + 1][k + A[i]] = max(dp[j + 1][k + A[i]], dp[j][k] + B[i]);
            }
        }
    }
    ll ans = 1ll << 60;
    for(int i = 1; i <= N; i++){
        for(int j = 100 * i; j >= 0; j--){
            if(X * i <= j) ans = min(ans, s - dp[i][j]);
        }
    }
    if(ans >> 60) ans = -1;
    cout << ans << '\n';
}