Program to calculate factorial of given number

#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
 //Program to calculate factorial of given number
  int a,n;
  double res;
  cout<<"Enter Number = ";
  cin>>n;
  res=1;
  for(a=1;a<=n;a++)
  res=res*a;
  cout<<"The Factorial of Given number is ="<<res;
getch();
    return 0;
 
}