Convert even byte array to odd

[medatib531]

Hello, my question is as follows:
Say I have a 256-bit array, e.g.

'74ccc1643dd3d97236bc74d378692f9617f779e6d935a6df9e8d2fe161b1fed4'

This represents a large number which is even. I want to convert this to an odd number as efficiently as possible.
My intuition is that XORing the Least Significant bit of this would be the most efficient way.
How can I do this?