#include <bits/stdc++.h>
using namespace std;
int n, k, a[110], b[110], c[110];
map<int, int> f[110];

int main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++) cin >> a[i];
	for (int i = 1; i <= n; i++) cin >> b[i];
	for (int i = 1; i <= n; i++) c[i] = a[i] - k * b[i];
	f[0][0] = 0;
	for (int i = 0; i < n; i++) {
		for (auto pi : f[i]) {
			int j = pi.first;
			assert(pi.second == f[i][j]);
			// f[i+1][j]
			if (f[i+1].find(j) == f[i+1].end())
				f[i+1][j] = f[i][j];
			else 
				f[i+1][j] = max(f[i+1][j], f[i][j]);
			// f[i+1][j+c[i]]
			if (f[i+1].find(j+c[i+1]) == f[i+1].end())
				f[i+1][j+c[i+1]] = f[i][j] + a[i+1];
			else 
				f[i+1][j+c[i+1]] = max(f[i+1][j+c[i+1]], f[i][j] + a[i+1]);
		}
	}
	if (!f[n][0])
		cout << -1 << endl;
	else 
		cout << f[n][0] << endl;
	return 0;
}