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>
#include<string.h>
int main(void)
{
	int len,i,cnt;
	char s[11],ss[11];
	scanf("%s",s);
	len=strlen(s);
	cnt=0;
	for(i=0;i<len;i++){
		if(s[i]!='B'){
			ss[cnt]=s[i];
			cnt++;
		}
		else if(cnt>0){
			cnt--;
		}
	}
	ss[cnt]='\0';
	printf("%s\n",ss);
	return 0;
}