1842: TheAlmostLuckyNumbers

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.

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

Output the number of almost lucky numbers between a and b, inclusive.

1 10
14 14
1 100

3
1
39