Primes in Interval

Description:

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.

Sample Input:

10 20

Sample Output:

4

Sample Input:

23 23

Sample Output:

1

Sample Input:

271 566

Sample Output:

46