while True:
    h,w=map(int,input().split())
    if ([w,h]==[0,0]):
        exit()
    for i in range(h):
        if (i % 2 == 0):
            print('#.'*(w//2) + '#'*(w%2))
        else:
            print('.#'*(w//2) + '.'*(w%2))
    print()
