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: Wrong Answer)

#include <stdio.h>
int main(void){
    int a, b, c, f=2, s=1;
    scanf("%d%d%d", &a, &b, &c);
    
    a == 5 ? f-- : a == 7 ? s--:0;
    b == 5 ? f-- : b == 7 ? s--:0;
    c == 5 ? f-- : c == 7 ? s--:0;
    
    printf(f == 0 && s == 0 ? "YES\n": "NO\n");
    
    return 0;
}