while True:
    h, w = map(int, raw_input().split())
    if h == 0 and w == 0:
        break
    else:
        result = list()
        for i in range(h):
            temp = list()
            if i % 2 == 0:
                even, odd = '#', '.'
            else:
                even, odd = '.', '#'
            for j in range(w):
                if j % 2 == 0:
                    temp.append(even)
                else:
                    temp.append(odd)
            result.append(temp)
        for i in result:
            print("".join(j for j in i))
        print("")