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 int lCommonPrefixOfCharIterators(CharacterIterator it1, CharacterIterator it2) {
  int n = 0;
  while (true) {
    if (!it1.hasNext() || !it2.hasNext()) return n;
    char a = it1.next(), b = it2.next();
    if (a != b) return n;
    ++n;
  }
}

static int lCommonPrefixOfCharIterators(CharacterIterator it1, CharacterIterator it2, CharComparator comparator) {
  if (comparator == null) return lCommonPrefixOfCharIterators(it1, it2);
  int n = 0;
  while (true) {
    if (!it1.hasNext() || !it2.hasNext()) return n;
    char a = it1.next(), b = it2.next();
    if (comparator.compare(a, b) != 0) return n;
    ++n;
  }
}
abstract static class CharacterIterator {
  abstract boolean hasNext();
  abstract char next();
}static interface CharComparator {
  int compare(char a, char b);
}
}