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 java.util.function.*;
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 java.awt.geom.*;
import javax.imageio.*;
import java.math.*;
class main {

static List<String> letterSeqOnlyTok(String s) {
  return singlePredTok(__6 -> isLetter(__6), s);
}
static List<String> singlePredTok(ICharPred isPartOfToken, String s) {
  ArrayList<String> tok = new ArrayList();
  int l = s == null ? 0 : s.length();
  
  int i = 0, n = 0;
  while (i < l) {
    int j = i;
    char c;
    
    // scan for whitespace
    while (j < l) {
      c = s.charAt(j);
      if (isPartOfToken.get(c))
        break;
      else
        ++j;
    }
    
    tok.add(substring(s, i, j));
    i = j;
    if (i >= l) break;

    // scan for non-whitespace
    
    do
      ++j;
    while (j < l && isPartOfToken.get(s.charAt(j)));

    tok.add(substring(s, i, j));
    i = j;
  }
  
  if ((tok.size() % 2) == 0) tok.add("");
  return tok;
}


static boolean isLetter(char c) {
  return Character.isLetter(c);
}




static String substring(String s, int x) {
  return substring(s, x, strL(s));
}

static String substring(String s, int x, int y) {
  if (s == null) return null;
  if (x < 0) x = 0;
  int n = s.length();
  if (y < x) y = x;
  if (y > n) y = n;
  if (x >= y) return "";
  return s.substring(x, y);
}



// convenience method for quickly dropping a prefix
static String substring(String s, CharSequence l) {
  return substring(s, lCharSequence(l));
}




static int strL(String s) {
  return s == null ? 0 : s.length();
}


static int lCharSequence(CharSequence s) {
  return s == null ? 0 : s.length();
}




interface ICharPred {
  boolean get(char c);
}

}