Contest1470/1470L.py

while True:
    h, w = map(int, input().strip().split())
    if h == w == 0: break
    for x in range(h):
        for y in range(w):
            if (x + y) % 2 == 0:
                print('#', end="")
            else:
                print(".", end="")
        print("")
    print("")