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 <A> boolean syncClear_trueIfChanged(Collection<A> c) {
  if (c == null) return false;
  synchronized(collectionMutex(c)) {
    if (c.isEmpty()) return false;
    c.clear();
    return true;
  }
}
// TODO: JDK 17!! ?? No! Yes? Yes!!

static Object collectionMutex(List l) {
  return l;
}

static Object collectionMutex(Object o) {
  

  if (o instanceof List) return o;
  
  // TODO: actually use our own maps so we can get the mutex properly
  
  String c = className(o);
  
    
  
    
  
  return o;
}




static String className(Object o) {
  return getClassName(o);
}




static String getClassName(Object o) {
  return o == null ? "null" : o instanceof Class ? ((Class) o).getName() : o.getClass().getName();
}



}