#include <iostream>
#include <fstream>
#include <string>
using namespace std;

class LineReader {
  public:
    // return whether there's another line
    boolean hasNextLine ();
    // return the words in the next line
    string[] nextLineWords ();
}

class Record {
  public:
    // a record with no occurrences
    Record (string);
    // get the word of this record
    string getWord ();
    // add another occurrence on given line
    void increment (int lineNum);
    // e.g., "is 5: 1 2 3"
    string toString();
}

class TreeNode {
  public:
    // a node with no occurrences
    TreeNode(string word, int lineNum);
    // insert a word on the given line into the tree
    void insert(string word, int lineNum);
    // build and return the final output
    string getFrequencyList();
}

// construct the tree, return the alphabetized list
int main () {

}