#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

int main(int argc, char const *argv[]) {
  ll n, x;std::cin >> n >> x;
  vll a(n), b(n);
  re(i, n) scanf("%lld", &a[i]);
  re(i, n) scanf("%lld", &b[i]);

  vvl minus, plus;
  for(int i=0;i<n;i++){
    a[i]-=x;
    if(a[i]<=0) minus.push_back({abs(a[i]), b[i]});
    else plus.push_back({a[i], b[i]});
  }

  //kを作るのに必要なお金
  ll m = minus.size();
  ll p = plus.size();
  ll INF = 10000000000;
  vvl dp = VV(m+1, 50001, INF, ll);
  vvl dp2 = VV(p+1, 50001, INF, ll);
  if(m!=0)dp[0][0] = 0;
  if(p!=0)dp2[0][0] = 0;

  for(int i=0;i<m;i++){
    ll val = minus[i][0], w = minus[i][1];
    for(int j=0;j<50001;j++){
      //スルー
      dp[i+1][j] = min(dp[i+1][j], dp[i][j] + w);
      //取る
      if(j+val<=50000) dp[i+1][j+val] = min(dp[i+1][j+val], dp[i][j]);
    }
  }

  for(int i=0;i<p;i++){
    ll val = plus[i][0], w = plus[i][1];
    for(int j=0;j<50001;j++){
      //スルー
      dp2[i+1][j] = min(dp2[i+1][j], dp2[i][j] + w);
      //取る
      if(j+val<=50000) dp2[i+1][j+val] = min(dp2[i+1][j+val], dp2[i][j]);
    }
  }
  for(int i=1;i<=50000;i++) dp[m][i] = min(dp[m][i], dp[m][i-1]);
  for(int i=50000-1;i>=0;i--) dp2[p][i] = min(dp2[p][i], dp2[p][i+1]);

  //for(int i=0;i<=10;i++) std::cout << dp2[p][i] << (i==10?"\n":" ");
  //for(int i=0;i<=10;i++) std::cout << dp[m][i] << (i==10?"\n":" ");

  ll ans = INF;
  for(int i=0;i<=50000;i++){
    ans = min(ans, dp2[p][i] + dp[m][i]);
  }
  std::cout << (ans==INF?-1:ans) << '\n';
  return 0;
}