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: cut : glass. vacuum : ?
Example Output: vacuum

Example Input: mop : mop. spread : ?
Example Output: knife

Example Input: cut : knife. wash : ?
Example Output:
soap