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.*;
// persistable (if you set "operation", make sure it's with a
// persistable object)
class main {

static class AllOnAllOperation<A, B> implements Steppable {
  Producer<Pair<A, B>> allOnAll; // e.g. an instance of AllOnAll<A, B>
  
  AllOnAllOperation() {}
  AllOnAllOperation(Producer<Pair<A, B>> allOnAll, IVF2<A, B> operation) {
  this.operation = operation;
  this.allOnAll = allOnAll;}
  
   IVF2<A, B> operation;
void operation(A a, B b) { if (operation != null) operation.get(a, b); else operation_base(a, b); }
final void operation_fallback(IVF2<A, B> _f, A a, B b) { if (_f != null) _f.get(a, b); else operation_base(a, b); }
void operation_base(A a, B b) {}

  public boolean step() {
    Pair<A, B> p = allOnAll.next();
    if (p == null) return false;
    operation(p.a, p.b);
    return true;
  }
}
static interface Producer<A> {
  public A next(); // null when end
}static interface Steppable {
  public boolean step(); // return false if done
}static interface IVF2<A, B> {
  void get(A a, B b);
}static class Pair<A, B> implements Comparable<Pair<A, B>> {
  A a;
  B b;

  Pair() {}
  Pair(A a, B b) {
  this.b = b;
  this.a = a;}
  
  public int hashCode() {
    return hashCodeFor(a) + 2*hashCodeFor(b);
  }
  
  public boolean equals(Object o) {
    if (o == this) return true;
    if (!(o instanceof Pair)) return false;
    Pair t = (Pair) o;
    return eq(a, t.a) && eq(b, t.b);
  }
  
  public String toString() {
    return "<" + a + ", " + b + ">";
  }
  
  public int compareTo(Pair<A, B> p) {
    if (p == null) return 1;
    int i = ((Comparable<A>) a).compareTo(p.a);
    if (i != 0) return i;
    return ((Comparable<B>) b).compareTo(p.b);
  }
}

static int hashCodeFor(Object a) {
  return a == null ? 0 : a.hashCode();
}
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);
}

}