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