hdoj1001--Sum Problem

import java.util.*;
import java.io.*;

class Main
{
    public static int sum(int n) {
        if(n % 2 == 0) return n/2*(n+1);
        else return (n+1)/2*n;
        
    }
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);
        int n;
        while(cin.hasNextInt()) {
            n = cin.nextInt();
            System.out.println(sum(n));
            System.out.println();
        }
    }
}

#include <stdio.h>

int sum(int n)
{
    if(n % 2) 
        return (n + 1) / 2 * n;
    else
        return (n / 2) * (n + 1);
}

int main()
{
    int n;
    while(scanf("%d",&n) != EOF){
        printf("%d\n\n",sum(n));
    }
    return 0;
}