#!/usr/bin/env python
# Author: Sean B. Palmer, inamidst.com
# License: LGPL, share and enjoy!
# About: http://inamidst.com/proj/primes/about

from mathfun import isprime

primes = [2, 3, 5, 7]

done = 0
while True: 
   if len(primes) == 1: 
      break
   first, primes = primes[0], primes[1:]
   for digit in '123456789': 
      n = int(digit + str(first))
      if isprime(n): primes.append(n)
   done += 1
   if (done % 100) == 0: 
      print 'done:', done, primes[-1]

print primes[0]