Problem:
Score : 100 points

Problem Statement

There are N children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give 1 candy to the first child in the line, 2 candies to the second child, ..., N candies to the N-th child. How many candies will be necessary in total?

Constraints

1≦N≦100

Input

The input is given from Standard Input in the following format:

N

Output

Print the necessary number of candies in total.

Sample Input 1

3

Sample Output 1

6

The answer is 1+2+3=6.

Sample Input 2

10

Sample Output 2

55

The sum of the integers from 1 to 10 is 55.

Sample Input 3

1

Sample Output 3

1

Only one child. The answer is 1 in this case.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
#include <string>
#include <cmath>
#include <ctype.h>
#include <map>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <cctype>
#include <queue>
#define REP(i,n) for(int i=0;i<(int)n;++i)
#define REP1(j,n) for(int j=0;j<(int)n;++j)
#define REPD(i,n) for(int i=n;i>=0;--i)
#define REPD1(j,n) for(int j=n;j=>0;--j)
#define REPS(i,n) for(int i=1;i<=(int)n;++i)
#define REPS1(j,n) for(int j=1;j<=(int)n;++j)
#define rep(i,a,n) for(int i=a;i<=(int)n;++i)
#define SZ(x) ((int)(x).size())	//size() unsigned -> int
#define DescSort(a) sort(a.begin(),a.end(),std::greater<int>())

using namespace std;
typedef long long ll;
const ll INF=1e9+7;

int main(void) {
	int n;
	cin >> n;
	cout << n * (n + 1) / 2 << endl;
	return 0;
}