#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n, x;
  cin >> n >> x;

  vector<int> a(n), b(n);
  REP (i, n) cin >> a[i];
  REP (i, n) cin >> b[i];

  if (x > *max_element(a.begin(), a.end())) {
    cout << -1 << endl;
    return 0;
  }
  
  vector<int> cost, value;
  int ret = 0;
  int c = 0;
  REP (i, n) {
    if (a[i] >= x) {
      c += a[i] - x;
    } else {
      cost.push_back(x - a[i]);
      value.push_back(b[i]);
      ret += b[i];
    }
  }

  vector<int> dp(c + 1);
  REP (i, cost.size()) {
    for (int j = c; j >= cost[i]; j--)
      dp[j] = max(dp[j], dp[j - cost[i]] + value[i]);
  }

  ret -= dp[c];
  cout << ret << endl;
  
  return 0;
}