**A - Deletable Primes**

**Problem**

A deletable prime is a prime such
that you can delete the digits one at a time, in some order, and get a prime at
each step. For instance, the number 4125673 is a deletable prime, since all
numbers in the sequence:

41**2**5673

4**1**5673

4567**3**

4**5**67

**4**67

**6**7

7

are also (deletable) primes.

Our objective is to print the
largest deletable prime in a given range.

**Input**

The input will consist of a
series of pairs of positive integers i and j, one pair of integers per line.
All integers will be less than 10,000,000. You can assume that i is lesser or
equal than j. You should process all pairs of integers, and for each pair
determine the largest deletable prime between i and j, inclusive. Input is
terminated by a line with the number -1.

**Output**

For each pair of input integers,
defining a range, you should output the largest deletable prime in the range,
or **none** if no deletable primes
exist in the range.

**Sample
Input**

**1 100**

**1000 1010**

**4125673
4125673**

**1 9999999**

**-1**

**Sample
Output**

**97**

**none**

**4125673**

**9999907**