def find_shape(bottom_lines, max_len):
    """
    Finds a shape of lowest horizontal lines with step=1
    :param bottom_lines:
    :param max_len:
    :return: list of levels (row values), list indexes are columns
    """
    shape = [1] * max_len
    for i in range(max_len):
        for line in bottom_lines:
            if line[0] <= i + 1 < line[2]:
                shape[i] = line[1]
                break
    return shape