Days without a weekly holiday

Problem

A warehouse numbers its days 1, 2, 3, and so on. Every 7th day (7, 14, 21, ...) is a holiday. Given the first day a and the last day b, count the days from a to b, both included, that are not holidays.

Input, output and limits

Input: One line: two integers a and b.
Output: One integer: the number of days from a to b that are not multiples of 7.
Constraints: 1 ≤ a ≤ b ≤ 10^9

Examples

Example

Input

5 15

Output

Days 5 to 15 are 11 days. Days 7 and 14 are holidays, so 9 remain.

Hints

Try the problem first. Open one hint at a time.

Hint 1

Counting day by day is too slow when b is a billion. Count how many multiples of 7 are in the range instead.

Hint 2

Multiples of 7 up to x are x // 7. Subtract the count up to a - 1 from the count up to b.

Write your Python code, run it on the examples and submit it to hidden tests.

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