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<cstdlib>
#include<map>
#include<iomanip>
#include<sstream>
#include<vector>
#include<stack>
#include<math.h>
#include<queue>
#include<complex>
using namespace std;

long long int solve(long long int n){
	if(n==2){return 3;}
	else if(n==4||n==6||n==9||n==11){return 2;}
	else{return 1;}
}

int main() {
	long long int n=1,m,a,b,c,d,e;
	long double z,w;
	string str,str2,str3;
	char ch;
	long long int x[130]={};
	cout << fixed << setprecision(10);
	cin>>a;
	cout<<a*(a+1)/2;


	cout<<endl;
}