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

public class Main {
    static Point[] points;
    static int[][] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int x = sc.nextInt();
        points = new Point[n];
        int total = 0;
        boolean enable = false;
        for (int i = 0; i < n; i++) {
            points[i] = new Point(x - sc.nextInt());
            total += points[i].value;
            enable |= (points[i].value <= 0);
        }
        if (!enable) {
            System.out.println(-1);
            return;
        }
        if (total <= 0) {
            System.out.println(0);
            return;
        }
        for (int i = 0; i < n; i++) {
            points[i].cost = sc.nextInt();
        }
        Arrays.sort(points);
        dp = new int[n][total + 1];
        for (int[] arr : dp) {
            Arrays.fill(arr, -1);
        }
        System.out.println(dfw(n - 1, total));
    }
    
    static int dfw(int idx, int total) {
        if (total <= 0) {
            return 0;
        }
        if (idx < 0 || points[idx].value <= 0) {
            return Integer.MAX_VALUE / 2;
        }
        if (dp[idx][total] < 0) {
            dp[idx][total] = Math.min(dfw(idx - 1, total), dfw(idx - 1, total - points[idx].value) + points[idx].cost);
        }
        return dp[idx][total];
    }
    
    static class Point implements Comparable<Point> {
        int value;
        int cost;
        
        public Point(int value) {
            this.value = value;
        }
        
        public int compareTo(Point p) {
            return value - p.value;
        }
    }
}
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 nextLine() throws Exception {
        return br.readLine();
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}