import javax.imageio.*;
import java.awt.image.*;
import java.awt.event.*;
import java.awt.*;
import java.security.NoSuchAlgorithmException;
import java.security.MessageDigest;
import java.lang.reflect.*;
import java.net.*;
import java.io.*;
import javax.swing.text.*;
import javax.swing.event.*;
import javax.swing.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.*;
import java.util.regex.*;
import java.util.List;
import java.util.zip.*;
import java.util.*;


abstract class Pred {
  boolean eval(Map<String, String> s);
}

public class main {
  static int nextMCellID;
  static Map<String, MCell> memoryCells = new TreeMap<String, MCell>();
  
  // a memory cell
  static class MCell {
    String id;
    Object value;
    long lastAccess;
    
    MCell(String id) {
  this.id = id;
      lastAccess = now();
    }
    
    Object get() {
      lastAccess = now();
      return value;
    }
    
    void set(Object value) {
      lastAccess = now();
      this.value = value;
    }
  }
  
  static MCell newMCell() {
    String id = "m" + ++nextMCellID;
    MCell cell = new MCell(id);
    memoryCells.put(id, cell);
    return cell;
  }
  
  static MCell getMCell(String id) {
    return memoryCells.get(id);
  }
  
  public static void main(String[] args) throws Exception {
    defineVerification("<memory cell> is occupied.",
      new Pred() {
        boolean eval(Map<String, String> s) {
          String cell = s.get("memory cell");
          return memoryCells.get(cell).get() != null;
        }
      });
    verify("m1 is occupied.");
  }
  
  static void defineVerification(String sentence, Pred p) {
  }

static long now_virtualTime;
static long now() {
  return now_virtualTime != 0 ? now_virtualTime : System.currentTimeMillis();
}


  static void set(Class c, String field, Object value) {
    try {
      Field f = set_findStaticField(c, field);
      f.setAccessible(true);
      f.set(null, value);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
  
  static Field set_findStaticField(Class<?> c, String field) {
    for (Field f : c.getDeclaredFields())
      if (f.getName().equals(field) && (f.getModifiers() & Modifier.STATIC) != 0)
        return f;
    throw new RuntimeException("Static field '" + field + "' not found in " + c.getName());
  }

static Object get(Object o, String field) {
  if (o instanceof Class) return get((Class) o, field);
  try {
    Field f = get_findField(o.getClass(), field);
    f.setAccessible(true);
    return f.get(o);
  } catch (Exception e) {
    throw new RuntimeException(e);
  }
}

static Object get(Class c, String field) {
  try {
    Field f = get_findStaticField(c, field);
    f.setAccessible(true);
    return f.get(null);
  } catch (Exception e) {
    throw new RuntimeException(e);
  }
}

static Field get_findStaticField(Class<?> c, String field) {
  for (Field f : c.getDeclaredFields())
    if (f.getName().equals(field) && (f.getModifiers() & Modifier.STATIC) != 0)
      return f;
  throw new RuntimeException("Static field '" + field + "' not found in " + c.getName());
}

static Field get_findField(Class<?> c, String field) {
  for (Field f : c.getDeclaredFields())
    if (f.getName().equals(field))
      return f;
  throw new RuntimeException("Field '" + field + "' not found in " + c.getName());
}
}