import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    static List<Integer> values = new ArrayList<>();
    static List<Integer> costs = new ArrayList<>();
    static int[][] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int target = sc.nextInt();
        int[] current = new int[n];
        for (int i = 0; i < n; i++) {
            current[i] = target - sc.nextInt();
        }
        int total = 0;
        for (int i = 0; i < n; i++) {
            int x = sc.nextInt();
            if (current[i] <= 0) {
                total -= current[i];
            } else {
                values.add(current[i]);
                costs.add(x);
            }
        }
        if (values.size() == n) {
            System.out.println(-1);
            return;
        }
        dp = new int[values.size()][total + 1];
        for (int[] arr : dp) {
            Arrays.fill(arr, -1);
        }
        System.out.println(dfw(values.size() - 1, total));
    }
    
    static int dfw(int idx, int v) {
        if (v < 0) {
            return Integer.MAX_VALUE / 2;
        }
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][v] < 0) {
            dp[idx][v] = Math.min(dfw(idx - 1, v) + costs.get(idx), dfw(idx - 1, v - values.get(idx)));
        }
        return dp[idx][v];
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}