while True:
    H,W = [int(i) for i in input().split()]
    if H == W == 0:
        break
    for h in range(H):
        for w  in range(w):
            if (h+w) % 2 == 0 :
                print('#', end ='')
            else
                print('.', end ='')
        print()
    print()