Mileposts

Andriy loves traveling by train. As he sits by the window, he keenly observes the passing landscape, paying special attention to the kilometer markers. He considers a marker "lucky" if its kilometer number, when divided by 7, leaves a remainder of 3. Your task is to write a program that calculates the number of "lucky" markers between two given markers, numbered from a to b.

Input

The program receives input in the form of two natural numbers 0 <= a < b <= 10^9, provided on a single line.

Output

The program should output the count of "lucky" markers.

Examples