#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N, X;
	cin >> N >> X;
	vector<int> A(N), B(N);
	REP(i, N) scanf("%d", &A[i]);
	REP(i, N) scanf("%d", &B[i]);
	
	// [i][j] := i 科目までみて {選んだ科目の評価の合計 - X} の和が j の最小コスト
	int offset = 99 * N;
	vector<int> dp(offset * 2 + 1, INF), ndp;
	int sum = 0;
	
	REP(i, N) {
		ndp.assign(offset * 2 + 1, INF);
		const int cur = A[i] - X;
		REP(j, dp.size()) {
			if (dp[j] == INF) continue;
			const int nex = j + A[i] - X;
			if (nex >= 0 && nex < ndp.size()) chmin(ndp[nex], dp[j]);
			chmin(ndp[j], dp[j] + B[i]);
		}
		chmin(ndp[offset + A[i] - X], sum);
		sum += B[i];
		swap(dp, ndp);
	}
	
	int ans = INF;
	FOR(i, offset, dp.size()) chmin(ans, dp[i]);
	if (ans == INF) puts("-1");
	else cout << ans << endl;
}