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<bits/stdc++.h>
using namespace std;
#define  ft  ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define  ll  long long
#define  pi  pair<int,int>
#define  pb  push_back
#define  F   first
#define  S   second
const int N=2e5+3;
//string s,p;
//vector<int>v;
//map<int,int>mp;

int main()
{
    ft
    ll t,i,j,n,m,l,r;
    cin>>n;
    n=(n*(n+1))/2;
    cout<<n<<"\n";
    return 0;
}