I have a new problem in my code I never seen before

Question

https://code.sololearn.com/c1g5EIRUj9Uy/?ref=app
Do I need to optimise it, and, if yes, then how?

If the problem was not caused by the optimisation issues, then, what do I have to do?

Answer 1

I tryed input:
5
1
5
Output gives 0, but no error.

Answer 2

Martin Taylor well, it is a question for my exam, I have to write code. The numbers in the first line are s = sum of coins we need, n = number of elements in array of the coins.

Each coin has its number, it can't be less than 0 or larger than 2*10⁶ , well, we have to sort them, and say, how many ways are here to have the number of s, where s=a[x]+a[y]

Answer 3

Coding Cat sorry, I forgot to type the input/output

1 attempt:
4 5
2 2 3 2 1

2 (but it cause error)

2 attempt:
5 3
5 4 1

1

3 attempt:
4 3
5 0 5

no output