Help me in solving LB08B problem

My issue

how he solved this question

Learning course: Beginner DSA in Python
Problem Link: CodeChef: Practical coding for everyone

@rakesh069

Correct Answer(s):

For N = 10 and M = 10, the number of extra shoes that Chef has to buy is 10.
For N = 5 and M = 10, the number of extra shoes that Chef has to buy is 5.
For N = 15 and M = 10, the number of extra shoes that Chef has to buy is 20.
Explanation:
N = 10
M = 10
Chef has 10 left shoes, only 10 right shoes are needed
The number of extra shoes that Chef has to buy is 10.

N = 5
M = 10
Chef has 10 left shoes, but no right shoes. So 5 right shoes are needed.
The number of extra shoes that Chef has to buy is 5.

N = 15
M = 10
Chef has 10 left shoes. To have 15 pairs, Chef needs 5 left shoes and 15 right shoes. So 20 shoes in total.
The number of extra shoes that Chef has to buy is 20.