[백준]8393_합

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class Main {
    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
 
        int N = Integer.parseInt(br.readLine());
 
        int sum = 0;
        for (int i = 1; i <= N; i++) {
            sum += i;
        }
        System.out.println(sum);
    }
}