while 1:
    H,W = map(int,input().split())
    if H == 0 and W == 0:
        break
    for i in range(H):
        if i%2 == 0:
            print('#.'*(W//2),'#'*(W%2),sep='')
        else:
            print('.#'*(W//2),'.'*(W%2),sep='')
    print()
