For technical reasons, some programming languages (Kotlin, C #) will not be available during round 877. ×

F. Primes in Interval
time limit per test
2 seconds
memory limit per test
64 megabytes
input
standard input
output
standard 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.

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