while True:
    H, W = map(int, input().split())
    if H == 0 and W == 0: break
    for x in range(int(H / 2)):
        print('#.'*int(W / 2))
        if W % 2 != 0: print("#")
        print('.#'*int(W / 2))
        if W % 2 != 0: print(".")
    if H % 2 != 0:
        print('#.'*int(W / 2))
        if W % 2 != 0: print("#")
    print()

