while True:
    a = list(map(int, input().split()))
    b = a[0]
    c = a[1]
    if b == c == 0:
        break
    for i in range(1, b+1):
        if i % 2 != 0:
            if c % 2 == 0:
                print('#.' * (c / 2))
            else:
                print('#.' * (c // 2) + '#')
        else:
            if c % 2 == 0:
                print('.#' * (c / 2))
            else:
                print('.#' * (c // 2) + '.')
    print()