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