while True:
    h, w = map(int, input().split())
    if h == 0 and w == 0:
        break
    else:
        elem = ("#", ".")
        for i in range(1, h+1):
            if i % 2 == 0:
                for j in range(1, w+1):
                    if j % 2 == 0:
                        print("#",end="")
                    else:
                        print(".",end="")
                print("")
            else:
                for j in range(1, w+1):
                    if j % 2 == 0:
                        print(".",end="")
                    else:
                        print("#",end="")
                print("")