Consider the tree:

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/8ac3cac9-e17f-4bd2-9288-ea430381665e/Untitled.png

Lowest common ancestor of nodes with value 1 and 4 is 2

Lowest common ancestor of nodes with value 1 and 5 is 3

Lowest common ancestor of nodes with value 2 and 4 is 4

Lowest common ancestor of nodes with value 1 and 2 is 2