args = input().split()
W, H = int(args[0]), int(args[1])
C = args[2]

for i in range(H):
    for j in range(W):
        if C == 'B':
            if (i + j) % 2 == 0:
                print('B', end='')
            else:
                print('W', end='')
        else:
            if (i + j) % 2 == 0:
                print('W', end='')
            else:
                print('B', end='')
    print()