#!/usr/bin/env python
     # encoding: utf-8
     
     import collections
     
     class Dictionary(object):
     
         def __init__(self, words):
             self.by_letter = collections.defaultdict(list)
             self.load_data(words)
     
         def load_data(self, words):
             by_letter = self.by_letter
             for word in words:
                 by_letter[word[0]].append(word)