PROBLEM LINK: Problem
Author and editorialist: Denis Anishchenko
Tester: Hasan Jaddouh
DIFFICULTY: Simple
PREREQUISITES: Basic maths
EXPLANATION:
If X is divisible by 10 then the answer is 0. If X is divisible only by 5 then the answer is 1, because after the first multiplying X will be divisible by 10. Otherwise, the answer is -1, because we will never get 5 by multiplying on 2.