# New Game

Students often find themselves studying only during exam periods, enjoying life in between. In this spirit, the students of the Faculty of Cybernetics have decided to take a break from computer games and have created a new board game called "Number Lotto." This game involves a set of tickets, each represented by a sheet of paper listing consecutive natural numbers within a specified integer interval [L, R]. For instance, a ticket with L=2 and R=10 would display the numbers 2, 3, 4, 5, 6, 7, 8, 9, 10.

The game unfolds over several rounds. In the first round, the host always announces the number 2. In each subsequent round, the host calls out a number that is one greater than the previous round's number. After the host announces a number i in a round, players must cross out all numbers on their ticket that are divisible by i without a remainder. Importantly, players only cross out numbers that have not been previously crossed out. The game continues as long as there is at least one uncrossed number remaining on the ticket.

Consider a ticket with L=2 and R=10. Initially, the ticket displays the numbers 2, 3, 4, 5, 6, 7, 8, 9, 10. In the first round, the host calls out the number 2, prompting the player to cross out 2, 4, 6, 8, and 10, leaving 3, 5, 7, and 9 uncrossed. In the second round, the host calls out 3, and the player crosses out 3 and 9, leaving 5 and 7. In the third round, the host calls out 4, but the player crosses out nothing. In the fourth round, the host calls out 5, and the player crosses out 5. In the fifth round, the host calls out 6, and again, the player crosses out nothing. Finally, in the sixth round, the host calls out 7, and the player crosses out the last remaining number, 7. Thus, the game for this ticket concludes after 6 rounds.

Your task is to determine the maximum number of rounds that the given ticket can be played.

## Input

The input consists of a single line containing two integers `L`

and R (2 ≤ L ≤ R ≤ 10^9).

## Output

Output a single integer representing the maximum number of rounds that the given ticket can be played.