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){
	char s[11],t[11]={},rev[11];
	int b=0;
	scanf("%s",s);
	int i,j=0;
	for(i=0;s[i]!='\0';i++);
	while(i>0){
		i--;
		if((b==0)&&(s[i]!='B')){
			rev[j]=s[i];
			j++;
		}else if(s[i]=='B') b++;
		else b--;
	}
	rev[j]='\0';
	j=0;
	for(i=0;rev[i]!='\0';i++);
	while(i>0){
		i--;
		t[j]=rev[i];
		j++;
	}
	t[j]='\0';
	printf("%s",t);
	return 0;
}