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;
 
typedef long long ll;
typedef double D;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
 
#define rd(x) scanf("%d",&x)
#define rd2(x,y) scanf("%d %d",&x,&y)
#define rl(x) scanf("%lld",&x)
#define rl2(x,y) scanf("%lld %lld",&x,&y)
#define wd(x) printf("%d" ,x)
#define wd2(x,y) printf("%d %d",x,y)
#define wl(x) printf("%lld",x)
#define wl2(x,y) printf("%lld %lld",x,y)
#define PC(x) putchar(x)
#define GC() getchar()
#define NL printf("\n")
#define SP printf(" ")
 
#define F first
#define S second
#define MP make_pair
#define PB push_back
 
#define fr(i,s,e) for(int i=s;i<e;i++)
#define frr(i,s,e) for(int i=s-1;i>=e;i--)
#define frv(i,a) for(int i = 0;i<(int)a.size();i++)
#define frvr(i,a) for(int i = a.size()-1;i>=0;i--)
#define tr(i,a) for(typeof(a.begin()) i = a.begin(); i != a.end();i++)
int main(){
	ll n;
	rl(n);
	wl(n*(n+1)/2);
	return 0;
}