Write a program which takes a very large number of 64-bit binary words and calculate the partity of word. The parity of the word is 1 if the number of 1 is in the word is odd; otherwise, it is 0.

Brute force approach:

```
def parity(x):
total = 0
while x:
total ^= x & 1
x >>= 1
return total
```

This solution runs in *O(n)* time, where *n* is the size of the word *x*.