def count_increases_in_window(numbers, window_length=3):
    """Count number of times sum of the window with window_length increases."""
    increases = 0
    for index, _ in enumerate(numbers[:-window_length]):
        prev_window = sum(numbers[index:index + window_length])
        cur_window = sum(numbers[index + 1:index + window_length + 1])
        if cur_window > prev_window:
            increases += 1
    return increases