T = '#.'

while True:
    H, W = [int(n) for n in input().split()]
    n, r = divmod(W, 2)
    if H==W==0:
        break
    for i in range(H):
        if i%2==0:
            print(T*n + T[0]*r)
        else:
            print(T[::-1]*n + T[-1]*r)
    print()

