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 (GCC 5.4.1) (judge verdict: Accepted)


#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <math.h>

#define MOD 1000000007
#define REP(i,n) for ((i)=0;i<(n);i++)
#define SET(a,c) memset(a,c,sizeof a)
#define CLR(a) memset(a,0,sizeof a)
#define MIN(a,b) (a>b?b:a)
#define MAX(a,b) (a>b?a:b)
#define LL long long
#define ULL unsigned long long



int main(void) {

	long ans = 0;
	int n,i;
	scanf("%d", &n);

	for(i = 1; i<=n;i++){
		ans += i;
	}

	printf("%ld", ans);


	return 0;
}

/* 最後の改行忘れるな！！ */