pattern = {
        0:["#", "."],
        1:[".", "#"],
    }

while True:
    (H, W) = map(int, raw_input().split())
    if H == W == 0:
        break
    for j in range(H):
        p = pattern[j % 2]
        print ("join([p[i % 2] for i in range(W)]))
    print()