Description

Count the number of times the digit $7$ appears among all integers in the given range [$L$, $R$].
For example, in the range [$60$, $80$], the digit $7$ appears $12$ times: in the units place of $67$ and $77$, and in the tens place of $70$ to $79$.

Input Format

A single line with two numbers $L$ and $R$ representing the range, separated by a space.

Output Format

An integer representing the number of times the digit $7$ appears.

Sample

60 80

12