Two analogies that relate actions to the tools used to perform the action is given in the form "A : B. C : ?". "A : B" relates action A to tool B. Your task is to replace the question mark (?) with the appropriate tool for the given action C, following the "A : B" relation.

Example Input: mop : mop. scrub : ?
Example Output: brush

Example Input: type : keyboard. unlock : ?
Example Output: key

Example Input: vacuum : vacuum. mop : ?
Example Output:
mop

