description: Monocarp is playing a computer game. Now he wants to complete the first level of this game.
  
  A level is a rectangular grid of 2 rows and n columns. Monocarp controls a character, which starts in cell (1, 1) — at the intersection of the 1-st row and the 1-st column.
  
  Monocarp's character can move from one cell to another in one step if the cells are adjacent by side and/or corner. Formally, it is possible to move from cell (x_1, y_1) to cell (x_2, y_2) in one step if |x_1 - x_2| ≤ 1 and |y_1 - y_2| ≤ 1. Obviously, it is prohibited to go outside the grid.
  
  There are traps in some cells. If Monocarp's character finds himself in such a cell, he dies, and the game ends.
  
  To complete a level, Monocarp's character should reach cell (2, n) — at the intersection of row 2 and column n.
  
  Help Monocarp determine if it is possible to complete the level.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 100) — the number of test cases. Then the test cases follow. Each test case consists of three lines.
  
  The first line contains a single integer n (3 ≤ n ≤ 100) — the number of columns.
  
  The next two lines describe the level. The i-th of these lines describes the i-th line of the level — the line consists of the characters '0' and '1'. The character '0' corresponds to a safe cell, the character '1' corresponds to a trap cell.
  
  Additional constraint on the input: cells (1, 1) and (2, n) are safe.
  
  Output
  
  For each test case, output YES if it is possible to complete the level, and NO otherwise.
  
  Example
  
  Input
  
  
  4
  3
  000
  000
  4
  0011
  1100
  4
  0111
  1110
  6
  010101
  101010
  
  
  Output
  
  
  YES
  YES
  NO
  YES
  
  Note
  
  Consider the example from the statement.
  
  In the first test case, one of the possible paths is (1, 1) → (2, 2) → (2, 3).
  
  In the second test case, one of the possible paths is (1, 1) → (1, 2) → (2, 3) → (2, 4).
  
  In the fourth test case, one of the possible paths is (1, 1) → (2, 2) → (1, 3) → (2, 4) → (1, 5) → (2, 6).
solution: import java.io.*;
  import java.util.*;
  
  
  public class Main {
      static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
      
      static class Point{
      	int x,y;
      	Point(int x, int y){
      		this.x = x;
      		this.y = y;
      	}
      }
  
      
      static int n = 2,m;
      static int board[][];
      public static void main(String[] args) throws Exception {
      	int T = Integer.parseInt(br.readLine());
      	while(T-- > 0) {
      		m = Integer.parseInt(br.readLine());
      		board = new int[n][m];
      		for(int i = 0; i<n; i++) {
      			String input = br.readLine();
      			for(int j = 0; j<m; j++) {
      				board[i][j] = input.charAt(j) - '0';
      			}
      		}
      		
      		bfs();
      		if(visited[n-1][m-1]) {
      			bw.write("YES\n");
      		}else {
      			bw.write("NO\n");
      		}
      	}
      	bw.flush();
      		
      }
      static boolean visited[][];
      static int dx[] = {0,1,0,-1,1,1,-1,-1};
      static int dy[] = {1,0,-1,0,1,-1,1,-1};
      static void bfs() {
      	Queue<Point> q = new LinkedList<Point>();
      	visited = new boolean[n][m];
      	q.add(new Point(0,0));
      	visited[0][0] = true;
      	while(!q.isEmpty()) {
      		Point p = q.poll();
      		for(int i = 0; i<8; i++) {
      			int nx = dx[i] + p.x;
      			int ny = dy[i] + p.y;
      			if(nx >= 0 && ny >= 0 && nx < n && ny < m && board[nx][ny] == 0 && !visited[nx][ny]) {
      				visited[nx][ny] = true;
      				q.add(new Point(nx,ny));
      			}
      		}
      	}
      }
  }