Bài 1

import java.util.Scanner;

public class P1 {

	public static int Sol(int n) {
		int s = 0;

		for (int i = 1; i <= n; i++)
			s += i;

		return s;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();

		System.out.println("S(" + n + ") = " + Sol(n));
	}
}