### Problem Statement

John thinks 4 and 7 are lucky digits, and all other digits are not lucky. A lucky number is a number that contains only lucky digits in decimal notation.

You are given ints a and b. Return the number of lucky numbers between a and b, inclusive.

### Definition

 Class: TheLuckyNumbers Method: count Parameters: int, int Returns: int Method signature: int count(int a, int b) (be sure your method is public)

### Constraints

-a will be between 1 and 1,000,000,000, inclusive.
-b will be between a and 1,000,000,000, inclusive.

### Examples

0)

 `1` `10`
`Returns: 2`
 There are only two lucky numbers among the first ten positive integers.
1)

 `11` `20`
`Returns: 0`
 But there are none among the next ten.
2)

 `74` `77`
`Returns: 2`
 These two numbers are lucky. There are no additional lucky numbers between them.
3)

 `1000000` `5000000`
`Returns: 64`

#### Problem url:

http://www.topcoder.com/stat?c=problem_statement&pm=8568

#### Problem stats url:

http://www.topcoder.com/tc?module=ProblemDetail&rd=12175&pm=8568

Vasyl[alphacom]

#### Testers:

PabloGilberto , Olexiy , marek.cygan , ivan_metelsky

Brute Force