You are given an n-by-n grid where each square is colored either black or white. A grid is correct if all of the following conditions are satisfied:
Given a grid, determine whether it is correct.
The first line contains an integer n (2≤n≤24; n is even). Each of the next n lines contains a string of length n consisting solely of the characters 'B' and 'W', representing the colors of the grid squares.
If the grid is correct, print the number 1 on a single line. Otherwise, print the number 0 on a single line.