import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner input = new Scanner(System.in); while(input.hasNext()){ int n = input.nextInt(); int sum = 0;
//暴力加合 for(int i=1; i<n+1; i++){ sum+=i; } System.out.println(sum); System.out.println(); } input.close(); } }