while True:
    [h, w] = map(int, (input().split()))
    if h==0 and w==0:
        break
    
    print(("#."*(w//2)+"#"*(w%2)+"\n"+".#"*(w//2)+"."*(w%2)+"\n")*(h//2)
            +("#."*(w//2)+"#"*(w%2)+"\n")*(h%2))
        