An integer is even when it is divisible by 2; otherwise it is odd.

Steps

1. Even means n = 2k for some integer k (last digit 0, 2, 4, 6, or 8).
2. Odd means n = 2k + 1 (last digit 1, 3, 5, 7, or 9).
3. Negatives follow the same rule: −6 is even, −3 is odd.