import java.util.Scanner;
public class AddFirstNNaturalNumber
{
    public static int Sum(int num)
    {
        if(num==0)
        {
            return 0;
        }
        else
        {
            return num+Sum(num-1);
        }
    }

    public static void main(String args[])
    {
        int num=0,sum=0;

        Scanner sc=new Scanner(System.in);
        System.out.print("ENTER Nth TERM ");

        num=sc.nextInt();
        sum=Sum(num);
        System.out.println("Sum of first "+num+" NATURAL NUMBER: "+sum);

    }

}