Programming in C

Write a program to calculate the factorial of a given number which is given by. Factorial of a given number n = n! = n*(n-1)*(n-2)*..*1

Using the above code of finding factorial write a code to calculate the permutation nPr with given values n and r (i.e) nPr = n! / (n-r)! You have to provide inputs for the values n and r