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("[p[i % 2] for i in range(W)]")
    print()