ArrayIndexOutOfBoundsException error while solving algorithm problem with Java.

package baekjun;

import java.util.Scanner;

public class problem6{
    static int M,N,K;
    static int[][] arr;
    static int[][] visited;
    static int testcase;


    public static void main(String[] args){
        int myX = 0;
        int myY = 0;

        Scanner sc = new Scanner(System.in);

        testcase = sc.nextInt();
        M = sc.nextInt();
        N = sc.nextInt();
        K = sc.nextInt();

        arr = new int[M][N];

        for (int i = 0; i < M; i++) {
            for (int j = 0; j < N; j++) {
                arr[i][j] = 0;
            }
        }

        for(int k = 0; k<testcase; k++) {
            int count = 0;

            for (int i = 0; i < K; i++){
                myX = sc.nextInt();
                myY = sc.nextInt();
                arr[myX][myY] = 1;
            }

            for(int i = 0; i<M; i++) {
                for (int j = 0; j<N; j++) {
                    if(arr[i][j] == 1) {
                        DFS(i, j);
                        count++;
                    }
                }
            }
            System.out.println(count);
        }
    }

    static void DFS(int x, int y){
        arr[x][y] = 0;

        if(arr[x+1][y] == 1 && x+1 < M) 
            DFS(x+1, y);
        if(arr[x][y+1] == 1 && y+1 < N) 
            DFS(x, y+1);
        if(arr[x-1][y] == 1 && x-1 >= 0) 
            DFS(x-1, y);
        if(arr[x][y-1] == 1 && y-1 >= 0) 
            DFS(x, y-1);
    }
}
}