CSES - HIIT Open 2017 - Labyrinth
• Time limit: 10.00 s
• Memory limit: 512 MB

You need to transport a stick through a 2-dimensional maze. The length of the stick is 5 meters and the width is 1 centimeter. The maze consists of blocks of size 1×1 meters. You cannot bend the stick, break it, or lift it. You can only slide it along the floor of the maze.

# Input

The first input line contains an integer t: the number of test cases. Then there are t test cases, described as follows:

First there is a line with two numbers, n and m, which indicates the size of the maze: n blocks tall and m blocks wide.

Then there is a line with two numbers, a and b, indicating the position of the entrance and exit, with 2 \le a \le m-1, and 2 \le b \le m-1. The entrance is in the top row, in column a, and the exit is in the bottom row, in column b.

Finally, there are n lines, with m characters on each row. The characters are either 0 or 1, indicating a block of empty space or a block of solid wall, respectively.

All blocks on the perimeter of the maze are walls, with the exception of the entrance and exit, which are empty.

# Output

Output t lines, one per test case. For each test case, output YES if there is a way to navigate the stick through the maze from the entrance to the exit, and NO otherwise.

# Limits

• 1 \le t \le 50
• 3 \le n \le 30
• 1 \le m \le 30

# Example

Here we have four test cases, the first one is illustrated above.

Input:

4
13 16
8 13
1111111011111111
1111111011110001
1111111011110001
1111111011110001
1111111011110001
1000000000000001
1000111011110111
1000111011110111
1000111011110111
1000000011110111
1000000011110111
1000000011110111
1111111111110111
13 16
8 13
1111111011111111
1111111011110001
1111111011110001
1111111011110001
1111111011110001
1000000000000001
1011111011110111
1011111011110111
1011111011110111
1011111011110111
1011111011110111
1000000011110111
1111111111110111
13 16
8 13
1111111011111111
1111111011111111
1111111011110001
1111111011110001
1111111011110001
1000000000000001
1000111011110111
1000111011110111
1000111011110111
1000000011110111
1000000011110111
1000000011110111
1111111111110111
1 3
2 2
101


Output:

YES
NO
NO
YES