题解 | #【模板】二分#

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

public class Main {
    static int N =(int)(1e5+10);
    static int n,q;
    static long[] a = new long[N];

    static int lowerBound(long[] a,int l,int r,long x) {
        while(l<r) {
            int mid = l+r>>1;
            if(x<=a[mid]) r=mid;
            else l = mid+1;
        }
        return l;
    }

    static int upperBound(long[] a,int l,int r,long x) {
        while(l<r) {
            int mid=l+r>>1;
            if(x<a[mid]) r=mid;
            else l=mid+1;
        }
        return l;
    }

    static void solve() {
        n = in.nextInt(); q = in.nextInt();
        for(int i=0;i<n;i++) {
            a[i] = in.nextLong();
        }
        while(q-->0) {
            int op = in.nextInt();
            int l = in.nextInt(), r = in.nextInt();
            long x = in.nextLong();
            int k=-1;
            if(op==1) {
                k=lowerBound(a,l,r,x);
            }else if(op==2) {
                k=upperBound(a,l,r,x);
            }else if(op==3){
                k=lowerBound(a,l,r,x)-1;
            }else {
                k=upperBound(a,l,r,x)-1;
            }
            if(k>=l&&k<r) out.println(a[k]);
            else 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());
        }
    }
}