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(){
    char s[11],out[11];
    int i,length,j=0;
    scanf("%s",s);
    length = sizeof s/sizeof s[0];

    for(i=0;i<length;i++){
        if(s[i]=='0')out[j]='0';
        if(s[i]=='1')out[j]='1';
        if(s[i]=='B')j--;
        j++;
    }

    printf("%s",out);

    return 0;
}