You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Two analogies that signify affordances are given in the form "A : B. C : ?". Affordance is the possibility of an action being done on an object, for example book is an affordance of writing. The phrase "A : B" implies that B is an affordance of A. Your task is to replace the question mark (?) with the appropriate affordance of the given action C, following the "A : B" relation. Your answer should be a single object without further explanation.

cure : disease. swing : ?
Solution: sword
Why? The given analogy implies that diseases can be cured - an affordance relation. Hence, the appropriate answer for swing is sword, since swords can be swung.

New input: paint : picture. sail : ?
Solution:
boat