using System;
public class Program
{
public static void Main()
Console.WriteLine("Hello World");
int x = 5;
int y=0;
recur(x, out y);
Console.WriteLine(y);
}
public static void recur(int n , out int res)
if(n==1)
res =1;
else
recur(n-1,out res);
res=n*res;