Hi, i didnt know how to use loop while twice, so i decided to use 'if'. I suppose that was a bad idea. In IntelliJ IDEA program works and prints good result. When I want to do this on this page , this print me following errors: Caused by: java.lang.ClassNotFoundException: pl.codegym.task.task04.task0433.Solution at java.net.URLClassLoader.findClass(URLClassLoader.java:382) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ... 3 more