#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  int N, X;
  cin >> N >> X;
  vector<int> A(N);
  vector<int> B(N);

  for (int i = 0; i < N; ++i) {
    cin >> A[i];
  }
  for (int i = 0; i < N; ++i) {
    cin >> B[i];
  }
  vector<int> C(N);
  int T = 0;
  int c_max = INT_MIN;
  for (int i = 0; i < N; ++i) {
    C[i] = A[i] - X;
    T += C[i];
    c_max = max(c_max, C[i]);
  }

  if (T >= 0) {
    cout << 0 << endl;
  } else if (c_max < 0) {
    cout << -1 << endl;
  } else {
    int L = abs(T);
    vector<ll> dp(L + 1, INT_MAX);
    dp[0] = 0;

    for (int idx = 0; idx < N; ++idx) {
      ll c = C[idx];
      if (c >= 0) continue;

      for (int i = L; i >= 0; --i) {
        ll ni = i + abs(c);
        if (ni > L) ni = L;

        ll n_cost = dp[i] + B[idx];
        dp[ni] = min(dp[ni], n_cost);
      }
    }

    ll ans = INT_MAX;

    for (int i = abs(T); i <= L; ++i) {
      ans = min(ans, dp[i]);
    }

    cout << ans << endl;
  }

  return 0;
}