import java.util.List;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.TreeSet;

public class exercises
{
  public List<String> sortByFirstLetter(List<String> words)
  {
    ArrayList<Queue> mahWords = new ArrayList<Queue>(26);
    for(String word:words)
    {
      int pos = Character.getNumericValue(word.toUpperCase().charAt(0)) - 65;
      if(mahWords.get(pos) == null)
        mahWords.set(pos, new LinkedList<String>());
      mahWords.get(pos).offer(word);
    }
    LinkedList ret = new LinkedList<String>();
    for(Queue<String> q:mahWords)
    {
      for(String word:q)
        ret.offer(word);
    }
    return ret;
  }
  public int busiestHour(List<PhoneCall> dayCalls)
  {
    TreeSet<PhoneCall> set = new TreeSet<PhoneCall>();
    for(PhoneCall call:dayCalls)
      set.add(call);
    return set.last().getStartHour();
  }
}