Python 3.3 NZEC (Pairwise AND Sum)

import math
import sys

n = 1
cases = 0
num = 0
arr = [0 for i in range(0,30)]
ans = 0


#print('Enter the test cases')
cases = int(input())

while cases:
    num = int(input())

    for i in range(0,30):

        if num % 2 == 1:
            arr[i] = arr[i] + 1
        num  = num // 2

        if num == 0:
            break
    cases-=1

#print('Arr: ',arr)
for i in range(0,30):
    if arr[i]:
        ans = ans + (n * arr[i] * (arr[i] - 1))//2
        n = n*2

print(int(ans))

Can some one tell me why am i getting NZEC.. This runs fine in idle