303414: CF661F. Primes in Interval

Memory Limit：64 MB Time Limit：2 S
Judge Style：Text Compare Creator：
Submit：0 Solved：0

Description

F. Primes in Intervaltime limit per test2 secondsmemory limit per test64 megabytesinputstandard inputoutputstandard output

You are given two integers a and b (a ≤ b). How many prime numbers are there on the interval from a to b, inclusive?

Input

The input contains two integers a and b (2 ≤ a ≤ b ≤ 1 000 000), separated by a single space.

Output

Output a single integer — the number of primes between a and b, inclusive.

ExamplesInput
10 20
Output
4
Input
23 23
Output
1
Input
271 566
Output
46

Input

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