#!/usr/bin/env python

import re, fileinput

r_num = re.compile(r'[ \t]{,5}(\d{3})(?:\.|:| To)')

f = None
for line in fileinput.input(): 
   m = r_num.match(line)
   if m: 
      num = m.group(1)
      if f: f.close()
      f = open('letter' + num + '.txt', 'w')
      f.write(line)
   elif f: f.write(line)

# EOF