TheAlmostLuckyNumbers | Topcoder Archive

Problem Statement

A lucky number is a number whose decimal representation contains only the digits 4 and 7. An almost lucky number is a number that is divisible by a lucky number. For example, 14, 36 and 747 are almost lucky, but 2 and 17 are not. Note that a number can be both lucky and almost lucky at the same time (for example, 747).

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

Definition

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

Constraints

a will be between 1 and 10,000,000,000, inclusive.
b will be between a and 10,000,000,000, inclusive.

Examples

```
1
```
```
10
```
```
Returns: 3
```
There are three almost lucky numbers less than or equal to ten - 4, 7 and 8.
```
14
```
```
14
```
```
Returns: 1
```
14 is an almost lucky number.
```
1
```
```
100
```
```
Returns: 39
```
```
1234
```
```
4321
```
```
Returns: 1178
```

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