while True:
    h, w = map(int, input().split())
    if h == w == 0:
        break
    for i in range(h):
        if i % 2 == 1:
            if w % 2 == 0:
                print('.#'*(w//2))
            elif w % 2 == 1:
                print('{}.'.format(".#"*(w//2)))
        if i % 2 == 0:
            if w % 2 == 0:
                print('#.'*(w//2))
            elif w % 2 == 1:
                print('{}#'.format('.#'*(w//2)))
    print()
