445A - DZY Loves Chessboard - CodeForces Solution

n , m = map(int, input().split())
chessBoard =[]
for i in range(n):
    chessBoard.append([y for y in input()])

for i in range(n):
    for j in range(m):
        if chessBoard[i][j] == "." :
            if((j+i)%2==0):
                chessBoard[i][j]='B';
            else:
                chessBoard[i][j]='W';
            
for x in chessBoard:
    for y in x:
        print(y,end = "")
    print()