Release 4.2.1 (fix divide by zero)
Release 4.2.1 (fix divide by zero)

SCNya/otus-java-2017-04-Alexeenko,SCNya/otus-java-2017-04-Alexeenko,SCNya/otus-java-2017-04-Alexeenko,SCNya/otus-java-2017-04-Alexeenko