#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using ld = long double;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,X; cin >> N >> X;
    vector<ll> A(N), B(N);
    rep(i,N) cin >> A[i];
    rep(i,N) cin >> B[i];
    ll SUMB = accumulate(B.begin(), B.end(), 0LL);

    ll ans = 1e18;
    int MAX_A = 500 * 100;
    vector<vector<ll>> dp(MAX_A + 1, vector<ll>(N + 1, -1e18));
    dp[0][0] = 0;
    rep(i,N) {
        vector<vector<ll>> nt = dp;
        for(int s = 0; s <= MAX_A; s++)
            for(int k = 0; k <= N; k++)
                if(s + A[i] <= MAX_A && k + 1 <= N) nt[s + A[i]][k + 1] = max(nt[s + A[i]][k + 1], dp[s][k] + B[i]);
        swap(dp, nt);
    }
    for(int n = 1; n <= N; n++) {
        for(int s = n * X; s <= MAX_A; s++) {
            ans = min(ans, SUMB - dp[s][n]);
        }
    }

    cout << (ans == ll(1e18) ? -1 : ans) << endl;
}