while true:
    (H,W) = [int(i) i in input().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()