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

    while True:
        (H, W) = [int(i) for i in 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()