import java.util.*; import java.util.zip.*; import java.util.List; import java.util.regex.*; import java.util.concurrent.*; import java.util.concurrent.atomic.*; import java.util.concurrent.locks.*; import java.util.function.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.text.*; import javax.swing.table.*; import java.io.*; import java.net.*; import java.lang.reflect.*; import java.lang.ref.*; import java.lang.management.*; import java.security.*; import java.security.spec.*; import java.awt.*; import java.awt.event.*; import java.awt.image.*; import java.awt.geom.*; import javax.imageio.*; import java.math.*; import java.time.Duration; import java.lang.invoke.VarHandle; import java.lang.invoke.MethodHandles; class main { static Steppable iteratorToSteppable(Iterator it) { return it == null ? null : new Steppable() { public boolean step() { if (!it.hasNext()) return false; it.next(); return true; } }; } // Note for implementors: It is allowed to call step() again // after it returned false (usually it should just return false again) static interface Steppable { public boolean step(); // return false if done } }