import java.io.*;
import java.util.*;

public class Main {
    static ArrayList<Integer> points = new ArrayList<>();
    static ArrayList<Integer> costs = new ArrayList<>();
    static int[][] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int x = sc.nextInt();
        int[] values = new int[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextInt() - x;
        }
        int total = 0;
        for (int i = 0; i < n; i++) {
            int c = sc.nextInt();
            if (values[i] >= 0) {
                total += values[i];
            } else {
                points.add(values[i]);
                costs.add(c);
            }
        }
        if (points.size() == n) {
            System.out.println(-1);
            return;
        }
        dp = new int[points.size()][total + 1];
        for (int[] arr : dp) {
            Arrays.fill(arr, -1);
        }
        System.out.println(dfw(points.size() - 1, total));
    }
    
    static int dfw(int idx, int price) {
        if (price < 0) {
            return Integer.MAX_VALUE / 2;
        }
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][price] < 0) {
            dp[idx][price] = Math.min(dfw(idx - 1, price) + costs.get(idx), dfw(idx - 1, price + points.get(idx)));
        }
        return dp[idx][price];
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}