while True:
    h, w = [int(i) for i in input().split()]
    
    if h == 0 and w == 0:
        break
    
    pattern = "#." * 151
    
    for i in range(h):
        line = pattern[:w] if i % 2 == 0 else pattern[1:w+1]
        print(line)

    print("")
