while True:
    h, w = map(int, input().split())
    if h == 0 and w == 0:break
    for i in range(h):
        if i % 2 == 0:
            print('#.'*(w // 2) + '#'*(w % 2))
        else:
            print('.#'*(w // 2) + '.'*(w % 2))
    print()
