NUMBER не позволяет в виде ответа задавать отрицательное число

[tatyderb]

NUMBER Число по индексу

int matrix[3][4] = {
    { 13, -7, 8, 5},
    {-7, -1, 14, 3},
    {1, -4, 2, 11}
};

Чему равно matrix[2][1]?

ANSWER: -4

дает
Traceback (most recent call last):
File "deploy.py", line 338, in
main()
File "deploy.py", line 326, in main
parse_lesson(str_list, param_dict, all_steps_to_one)
File "deploy.py", line 148, in parse_lesson
commit_step(steps, lesson_id, lines[line_from: line_to], param_dict)
File "deploy.py", line 36, in commit_step
st = from_lines(lines, param_dict)
File "C:\work\deploy_scripts\st_types\steps.py", line 40, in from_lines
st = StepNumber.num_from_md(text_lines)
File "C:\work\deploy_scripts\st_types\st_number.py", line 82, in num_from_md
ans = ans_template.parseString(line)
File "C:\Users\tatyd.conda\envs\edu\lib\site-packages\pyparsing.py", line 1955, in parseString
raise exc
File "C:\Users\tatyd.conda\envs\edu\lib\site-packages\pyparsing.py", line 4182, in parseImpl
raise maxException
pyparsing.ParseException: Expected {Combine:({W:(0123...) "." W:(0123...)}) ^ W:(0123...)}, found '-' (at char 8), (line:1, col:9)