def signed_int_str(input_int: int):
    """
    Converts an integer into a string that includes the integer's sign, + or -

    :param int input_int: the input integer to convert to a signed integer string
    :return str signed_int_str: the signed integer string
    """
    if input_int >= 0:
        return '+' + str(input_int)
    else:
        return str(input_int)