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