b20.cpp

#include<iostream>
using namespace std; 
   int factorial (int n){

       int fact=1;

       for(int i=1;i<=n;i++){
           fact=fact*i;

       }

       return fact;

   }


int main(){
      int a;
      
      cout<<"enter a  number "<<endl;
       cin>>a;

      cout<<"the factorial of the no. is "<<factorial(a);

    return 0;
}