Given an integer `n` return `"odd"` if the number of its divisors is odd. Otherwise return `"even"`.
**Note**: big inputs will be tested.
## Examples:
All prime numbers have exactly two divisors (hence `"even"`).
For `n = 12` the divisors are `[1, 2, 3, 4, 6, 12]` – `"even"`.
For `n = 4` the divisors are `[1, 2, 4]` – `"odd"`.
oddity=lambda n: ["odd","even"][n**.5%1!=0]
oddity=lambda n: ["odd","even"][n**.5%1!=0]