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