USING C++

Fadi has a safe with a lock that has 20 buttons that can each be clicked only once. Fadi remembers that the safe opens after clicking on 5 buttons but cant remember which 5 buttons. He decided to try every possible 5 buttons and wants to know how many trials he has to make.

Fadi knows from high school that this requires computing combinations (20C5 or 20 choose 5). So he wrote a program to compute n choose k for any 1 <= k <= n <= 20.

Fadis program can be simplified! Help Fadi improve his code by refactoring it to use functions:

Modify the code by implementing and using (at least) two functions.