A. Not Shadingtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputThere is a grid with n rows and m columns. Some cells are colored black, and the rest of the cells are colored white.In one operation, you can select some black cell and do exactly one of the following:   color all cells in its row black, or  color all cells in its column black. You are given two integers r and c. Find the minimum number of operations required to make the cell in row r and column c black, or determine that it is impossible.InputThe input consists of multiple test cases. The first line contains an integer t (1 \leq t \leq 100) — the number of test cases. The description of the test cases follows.The first line of each test case contains four integers n, m, r, and c (1 \leq n, m \leq 50; 1 \leq r \leq n; 1 \leq c \leq m) — the number of rows and the number of columns in the grid, and the row and column of the cell you need to turn black, respectively.Then n lines follow, each containing m characters. Each of these characters is either 'B' or 'W' — a black and a white cell, respectively.OutputFor each test case, if it is impossible to make the cell in row r and column c black, output -1. Otherwise, output a single integer — the minimum number of operations required to make the cell in row r and column c black. ExampleInput
93 5 1 4WBWWWBBBWBWWBBB4 3 2 1BWWBBWWBBWWB2 3 2 2WWWWWW2 2 1 1WWWB5 9 5 9WWWWWWWWWWBWBWBBBWWBBBWWBWWWBWBWBBBWWWWWWWWWW1 1 1 1B1 1 1 1W1 2 1 1WB2 1 1 1WBOutput
1
0
-1
2
2
0
-1
1
1
NoteThe first test case is pictured below.  We can take the black cell in row 1 and column 2, and make all cells in its row black. Therefore, the cell in row 1 and column 4 will become black.  In the second test case, the cell in row 2 and column 1 is already black.In the third test case, it is impossible to make the cell in row 2 and column 2 black.The fourth test case is pictured below.  We can take the black cell in row 2 and column 2 and make its column black.   Then, we can take the black cell in row 1 and column 2 and make its row black.   Therefore, the cell in row 1 and column 1 will become black.
93 5 1 4WBWWWBBBWBWWBBB4 3 2 1BWWBBWWBBWWB2 3 2 2WWWWWW2 2 1 1WWWB5 9 5 9WWWWWWWWWWBWBWBBBWWBBBWWBWWWBWBWBBBWWWWWWWWWW1 1 1 1B1 1 1 1W1 2 1 1WB2 1 1 1WB
1 0 -1 2 2 0 -1 1 1 
['constructive algorithms', 'implementation', '*800']