백준 8393번

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int sum = 0;

        for (int i = 0; i <= n; i++) {
            sum = sum + i;
        }
        System.out.println(sum);

          br.close();
    }
}

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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;


public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        int n = Integer.parseInt(br.readLine());
        br.close();
        int sum = 0;

        for (int i = 0; i <= n; i++)
            sum += i;

        System.out.println(sum);
    }
}