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 (Clang 10.0.0) (judge verdict: Wrong Answer)

#include<stdio.h>

int main(){
	char key[15];
	scanf("%s", key);
	int ctrb=0;
	int len=0;
	for(int i=0; key[i]!='\0'; i++){
		if(i>0){
			if(key[i]=='B'){
				if(key[i+1]=='B'){
					key[i-2]='f';
				}
				key[i-1]='f';
				ctrb++;
			}
			
		}
		else{
			if(key[i]=='B'){
				key[i]='f';
				ctrb++;
			}
		}
		len++;
	}
	for(int i=0; i<len; i++){
		if(key[i]=='1' || key[i]=='0'){
			printf("%c", key[i]);
		}
	}
	
	return 0;
}