Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = 'N'

import com.teamtreehouse.KaraokeMachine;
import com.teamtreehouse.model.Song;
import com.teamtreehouse.model.SongBook;

public class Karaoke {

  public static void main(String[] args) {
    SongBook songBook = new SongBook();
    KaraokeMachine machine = new KaraokeMachine(songBook);
    machine.run();
  }
}

package com.teamtreehouse;

import com.teamtreehouse.model.Song;
import com.teamtreehouse.model.SongBook;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class KaraokeMachine {
  private SongBook mSongBook;
  private BufferedReader mReader;
  private Map<String, String> mMenu;  

  public KaraokeMachine(SongBook songBook) {
    mSongBook = songBook;
    mReader = new BufferedReader(new InputStreamReader(System.in));
    mMenu = new HashMap<String, String>();
    mMenu.put("add", "Add a new song to the song book");
    mMenu.put("choose", "Choose a song to sing!");
    mMenu.put("quit", "Give up. Exit the program");
  }

  private String promptAction() throws IOException {
    System.out.printf("There are %d songs available. Your options are: %n",
                      mSongBook.getSongCount());
    for (Map.Entry<String, String> option : mMenu.entrySet()) {
      System.out.printf("%s - %s %n",
                        option.getKey(),
                        option.getValue());
    }
    System.out.print("What do you want to do: ");
    String choice = mReader.readLine();
    return choice.trim().toLowerCase();
  }

  public void run() {
    String choice = "";
    do {
      try {
        choice = promptAction();
        switch(choice) {
          case "add":
          Song song = promptNewSong();
          mSongBook.addSong(song);
          System.out.printf("%s added!   %N%N", song);
            break;
          case "choose":
            String artist = promptArtist();
            Song artistSong = promptSongForArtist(artist);
          // TODO: Add to a song queue
          System.out.printf("You chose: %s %n", artistSong);
            break;
          case "quit":
            System.out.println("Thanks for playing!");
            break;
          default: 
            System.out.printf("Unknown choice: %s'. Try again. %n%n%n", 
                              choice);
        }
      } catch (IOException ioe) {
        System.out.println("Problem with input");
        ioe.printStackTrace();
      }
    } while(!choice.equals("quit"));
  } 

    private Song promptNewSong() throws IOException {
      System.out.print("Enter the artist's name: ");
      String artist = mReader.readLine();
      System.out.print("Enter the title: ");
      String title = mReader.readLine();
      System.out.print("Enter the video URL: ");
      String videoUrl = mReader.readLine();
      return new Song(artist, title, videoUrl);
    }

  private String promptArtist() throws IOException {
    System.out.println("Available artists: ");
    List<String> artists = new ArrayList<>(mSongBook.getArtists());
    int index = promptForIndex(artists);
    return artists.get(index);    
  }

  private Song promptSongForArtist(String artist) throws IOException {
    List<Song> songs = mSongBook.getSongsForArtist(artist);
    List<String> songTitles = new ArrayList<>();
    for (Song song : songs) {
      songTitles.add(song.getTitle());
    }
    int index = promptForIndex(songTitles);
    return songs.get(index);
  }  

  private int promptForIndex(List<String> options) throws IOException {
    int counter = 1;
    for (String option : options) {
      System.out.printf("%d.) %s %n", counter, option);
      counter++;
    }
    String optionAsString = mReader.readLine();
    int choice = Integer.parseInt(optionAsString.trim());
    System.out.print("Your choice:  ");
    return choice -1;
  }
  }

package com.teamtreehouse.model;

public class Song {
  private String mArtist;
  private String mTitle;
  private String mVideoUrl;

  public Song(String artist, String title, String videoUrl) {
    mArtist = artist;
    mTitle = title;
    mVideoUrl = videoUrl;
  }

  public String getTitle() {
    return mTitle;
  }

  public String getArtist() {
    return mArtist;
  }

  public String getVideoUrl() {
    return mVideoUrl;
  }


  @Override
  public String toString() {
    return String.format("Song: %s by %s", mTitle, mArtist);
  }
}

package com.teamtreehouse.model;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class SongBook {
  private List<Song> mSongs;

  public SongBook() {
  mSongs = new ArrayList<Song>();
}

  public void addSong(Song song) {
    mSongs.add(song);
  }

  public int getSongCount() {
    return mSongs.size();
  }

  // FIXME: This should be cashed!
  private Map<String, List<Song>> byArtist() {
    Map<String, List<Song>> byArtist = new HashMap<>();
    for (Song song : mSongs) {
      List<Song> artistSongs = byArtist.get(song.getArtist());
      if (artistSongs == null) {
        artistSongs = new ArrayList<>();
        byArtist.put(song.getArtist(), artistSongs);
      }
      artistSongs.add(song);
    }
    return byArtist;
  }

  public Set<String> getArtists() {
    return byArtist().keySet();
  }

  public List<Song> getSongsForArtist(String artistName) {
    return byArtist().get(artistName);
  }

}