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<stdlib.h>
int N, *a;
int ave=0;
void input(){
    scanf("%d",&N);
    a=(int*)malloc(N);
    int i;
    for(i=0;i<N;i++){
        scanf("%d", &a[i]);
        ave+=a[i];
    }
    ave=ave/N;
}
int main(){
    int i, cost1=0, cost2=0;
    input();
    for(i=0; i<N;i++) cost1+=(a[i]-ave)*(a[i]-ave);
    for(i=0; i<N;i++) cost2+=(a[i]-ave-1)*(a[i]-ave-1);
    if(cost1<cost2) printf("%d\n",cost1);
    else printf("%d\n",cost2);
    
    return 0;
}