import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {

        System.out.println("Enter a number ");
        try (Scanner sc = new Scanner(System.in)) {
            int n = sc.nextInt();
            int result =  sum(n);
            System.out.println("Sum = " + result);
        }
    }

    static int sum(int n) {
        if (n != 0)
            return n + sum(n - 1);
        else
            return n;
    }
}