while True:
    h,w = map(int, input().split())
    if (h,w == 0):
        break
    for i in range(h):
        if i % 2 == 0:
            print("#."*(w//2) + "#"*(w%2))
        elif i % 2 == 1:
            print(".#"*(w//2) + "."*(w%2))
    print()
