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 Python (3.4.3) (judge verdict: Runtime Error)

import sys
import math
def i():return int(sys.stdin.readline().replace("\n",""))
def i2():return map(int,sys.stdin.readline().replace("\n","").split())
def s():return str(sys.stdin.readline().replace("\n",""))
def l():return list(sys.stdin.readline().replace("\n",""))
def intl():return [int(k) for k in sys.stdin.readline().replace("\n","").split()]
def lx():return list(map(lambda x:int(x)*-1,sys.stdin.readline().replace("\n","").split()))
def t():return tuple(map(int,sys.stdin.readline().replace("\n","").split()))

if __name__ == "__main__":pass

n = i()
a = intl()
if n == 1:print(0)
else:
    s = max(a)+min(a)
    k1 = s//2
    k2 = s//2 + s%2
    k3 = s//2 -1
    c1 = 0
    c2 = 0
    c3 = 0
    for i in range(n):
        c3 += (a[i]-k3)**2
        c2 += (a[i]-k2)**2
        c1 += (a[i]-k1)**2
    print(min(c1,c2,c3))