[백준] 8393번 : 합 - Java(자바)

https://www.acmicpc.net/problem/8393

import java.util.*;
public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int sum=0;
        if(n%2==1){
            int m=(n+1)/2;
            sum=(1+n)*(n/2)+m;
        } 
        else sum=(1+n)*((n+1)/2);
        System.out.print(sum);
    }
}