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.

Ex Input:
swat : fly. elect : ?

Ex Output:
president


Ex Input:
break : promise. sing : ?

Ex Output:
song


Ex Input:
climb : ladder. open : ?

Ex Output:

door