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 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 javax.imageio.*;
import java.math.*;
class main {

static class ExternalMutex /*implements AutoCloseable*/ {
  int referenceCount;
  
  void incRefCount() {
    referenceCount++;
    
  }
  
  int decRefCount() {
    --referenceCount;
    
    return referenceCount;
  }
  
  /*public void close {
    var map = externalMutexMap();
    synchronized(map) {
      if (--referenceCount == 0)
        map.remove(this);
    }
  }*/
}}