import java.io.*;
import java.util.*;
class More {
public static void main (String [] args) throws IOException {

    String s,wrd;
    Hashtable<String,MyWord> h = new Hashtable<String,MyWord>();
    ArrayList<String> sourcefilelist = new ArrayList<String>();    
  

    FileInputStream stream = new FileInputStream("/mnt/nfs/netapp1/fs3/kvaradar/.public-html/sp2010/hw7input/sourcefiles");
    InputStreamReader reader = new InputStreamReader(stream);
    StreamTokenizer tokens = new StreamTokenizer(reader);


    while (tokens.nextToken() != tokens.TT_EOF) {
	s = tokens.sval;
        sourcefilelist.add(s);

    }
    stream.close();

    String inputfilename, inputfilenameprefix;
    inputfilenameprefix = "/mnt/nfs/netapp1/fs3/kvaradar/.public-html/sp2010/hw7input/";
    StringBuilder sb;
    MyWord w;

    for( String x: sourcefilelist ) {
       System.out.println("Reading " + x);
       sb = new StringBuilder();
       sb.append(inputfilenameprefix);
       sb.append(x);
       inputfilename = new String(sb);
     
       stream = new FileInputStream(inputfilename);
       reader = new InputStreamReader(stream);
       tokens = new StreamTokenizer(reader);


       while (tokens.nextToken() != tokens.TT_EOF) {
	      s = tokens.sval;
              if (isGoodString(s) && (s.length() > 4)) {
		  w = h.get(s);
                  if (w != null) {
                      w.multiplicity = w.multiplicity + 1;
                      h.put(s, w);
		  }
                  else
                      h.put(s, new MyWord(s,1));
              }
       }
       stream.close();
    }

  

    Collection<MyWord> wordlist = h.values();
    for (MyWord v: wordlist) {
	if (v.multiplicity > 20) 
	    System.out.println(v.word);
    }

}

public static boolean isGoodString(String s) {



    if (s == null) return false;

    boolean isValid = true;
    int i = 0;
    while( (i < s.length()) && isValid ) {
    isValid = java.lang.Character.isLetter(s.charAt(i));
    i++;
    }
    return isValid;
}

}


class MyWord {

    String word;
    int multiplicity;

    public MyWord(String s, int x) {word = s; multiplicity = x;}
}