题解 | #请客吃饭#

import java.io.*;
import java.util.*;
import java.math.BigInteger;

public class Main {
    static int N = (int)(2e5 + 10);
    static int mx = Integer.MAX_VALUE;
    static int n;
    static long k;
    static int[] w = new int[N], h = new int[N];

    static void solve() {
        n = in.nextInt();
        k = in.nextLong();
        for (int i = 0; i < n; i++) {
            w[i] = in.nextInt();
        }
        for (int i = 0; i < n; i++) {
            h[i] = in.nextInt();
        }
        int[][] t = new int[n][2];
        for (int i = 0; i < n; i++) {
            t[i][0] = w[i];
            t[i][1] = h[i];
        }
        Arrays.sort(t, new Comparator<int[]>() {
            public int compare(int[] o1, int[] o2) {
                return o1[0] - o2[0];
            }
        });

        int l = 0;
        int r = 0;
        long sum = 0L;
        if (t[r][1] >= k) {
            System.out.print(0);
            return;
        }
        while (r != n) {
            while (r != n && sum < k) {
                sum += t[r][1];
                r++;
            }
            while (sum >= k) {
                mx = Math.min(mx, t[r - 1][0] - t[l][0]);
                sum -= t[l][1];
                l++;
            }
        }
        if (mx != Integer.MAX_VALUE) {
            System.out.print(mx);
            return;
        }
        out.println(-1);

    }

    public static void main(String[] args) {
        solve();
        out.flush();
    }

    static FastReader in = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);

    static class FastReader {
        static BufferedReader br;
        static StringTokenizer st;

        FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            String str = "";
            while (st == null || !st.hasMoreElements()) {
                try {
                    str = br.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
                st = new StringTokenizer(str);
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}