import java.util.*;

public class Main {
    static ArrayList<Unit> list = new ArrayList<>();
    static int[][] dp;
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int x = sc.nextInt();
    	int[] aArr = new int[n];
    	for (int i = 0; i < n; i++) {
    	    aArr[i] = sc.nextInt();
    	}
    	int sum = 0;
    	for (int i = 0; i < n; i++) {
    	    int y = sc.nextInt();
    	    if (aArr[i] < x) {
    	        list.add(new Unit(x - aArr[i], y));
    	    } else {
    	        sum += aArr[i] - x;
    	    }
    	}
    	if (list.size() == n) {
    	    System.out.println(-1);
    	    return;
    	}
    	int length = list.size();
    	dp = new int[length][sum + 1];
    	for (int[] arr : dp) {
    	    Arrays.fill(arr, Integer.MAX_VALUE);
    	}
    	System.out.println(dfw(length - 1, sum));
    }
    
    static int dfw(int idx, int sum) {
        if (sum < 0) {
            return Integer.MAX_VALUE / 10;
        }
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][sum] == Integer.MAX_VALUE) {
            dp[idx][sum] = Math.min(dfw(idx - 1, sum - list.get(idx).value), dfw(idx - 1, sum) + list.get(idx).cost);
        }
        return dp[idx][sum];
    }
    
    static class Unit {
        int value;
        int cost;
        
        public Unit(int value, int cost) {
            this.value = value;
            this.cost = cost;
        }
        
        
    }
}