while True:
    h, w = map(int, raw_input().split())
    if h == 0 and w == 0:
        break
    
    for i in range(0, h):
        wid = ""
        for j in range(0, w):
            if  (i+j)%2 == 0:
                wid += "#"
            else:
                wid += "."
        print wid

    print ""