//
//	read n, output 1+2+...+n
//		quit for 0 or negative input
//
import java.util.Scanner;
class OutSum
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);

		int n = input.nextInt();
		boolean done = false;

		while( !done )
		{
			int ans = sum(n);	// call the method
			System.out.println("ANS = " + ans);

			n = input.nextInt();
			if( n<=0 ) done = true;
		}

		System.out.println("\n\nDone.\n\n");
	}
	//------------------------------------
	// Calulate 1+2+...+N
	private static int sum(int N)
	{
		int temp=0;
		for(int i=0; i<=N; i++)
			temp += i;
		return temp;
	}
}