In c language please!! Also cannot use the long long factorial method

Write a program that calculates 5 combinations of n integers in groups of m given by the user. The program asks the user two positive integers; the total number n, and the number per groupm. Then, the program displays the number of combinations. The program repeats the procedure five times asking the two numbers, and calculating the combination.

What difficulty might prevent you from calculating the combinations of larger number; e.g. 13 or more?

Output sample: