/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int sum=recursiveSum(n);
        System.out.println("Sum of first "+n+" numbers : "+sum);
        sc.close();
	}
 
	public static int recursiveSum(int n){
	    if(n<=1){
	        return n;
	    }
	    return n+recursiveSum(n-1);
	}
}

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Ng==

6