Given an array of numbers which contains all even numbers except one, or all add numbers except one.

How do you find the different number?

For example consider the array `[1, 2, 3, 5, 9], 2`

is the different number.

Similarly in the array `[10, 6, 7, 24, 36], 7`

is the different number.

This problem was originally appeared on Codeforces.

This is a simple implementation problem, which can be solved in one iteration.

When we are reading numbers, just keep track of the following information.

- first even index
- first odd index
- even number count

At the end, check if the even number count is 1, If it is, then print first even index, otherwise print first odd index.

Here is the C++ code for this.