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 <A> AutoCloseable tempSetTL(ThreadLocal<A> tl, A a) {
  return tempSetThreadLocal(tl, a);
}


static <A> AutoCloseable tempSetThreadLocal(final ThreadLocal<A> tl, A a) {
  if (tl == null) return null;
  final A prev = setThreadLocal(tl, a);
  return new AutoCloseable() { public String toString() { return "tl.set(prev);"; } public void close() throws Exception { tl.set(prev); }};
}


static <A> AutoCloseable tempSetThreadLocalIfNecessary(ThreadLocal<A> tl, A a) {
  if (tl == null) return null;
  A prev = tl.get();
  if (eq(prev, a)) return null;
  tl.set(a);
  return new AutoCloseable() { public String toString() { return "tl.set(prev);"; } public void close() throws Exception { tl.set(prev); }};
}






static <A> A setThreadLocal(ThreadLocal<A> tl, A value) {
  if (tl == null) return null;
  A old = tl.get();
  tl.set(value);
  return old;
}


static boolean eq(Object a, Object b) {
  return a == b || a != null && b != null && a.equals(b);
}






static String str(Object o) {
  return o == null ? "null" : o.toString();
}

static String str(char[] c) {
  return new String(c);
}



}