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 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<string.h>

int main(){
    char s[100000];
    scanf("%s",s);
    int len=strlen(s);

    int i=0;
    int alpha[26]={0};
    for(int k=0;k<len;k++){
        alpha[s[k]-'a']++;
    }
    int max=alpha[0];
    for(int k=1;k<26;k++){
        if(alpha[k]>max){
            max=alpha[k];
        }
    }
    if(2*max<=len){
        while(2*max<=(len-i)){
            i++;
            for(int k=0;k<26;k++){
                alpha[k]=0;
            }
            for(int k=((i+1)/2);k<(len-i/2);k++){
                alpha[s[k]-'a']++;
            }
            int max=alpha[0];
            for(int k=1;k<26;k++){
                if(alpha[k]>max){
                    max=alpha[k];
                }
            }
        }
    }

    if(i==(len-1)){
        printf("%d %d",-1,-1);
    }else{
        printf("%d %d",i+1,len-i/2);
    }
    return 0;
}