Count Primes in a Range

You are given two integers L and R. Your task is to count the number of prime numbers in the interval [L, R].

The constraints are given as follows:

• $1 \leq L \leq R < 2^{31}$
• $R-L \leq 10^6$

Note: A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

inputFormat

The input consists of a single line with two space-separated integers L and R.

For example:

1 10

outputFormat

Output a single integer representing the number of prime numbers in the interval [L, R].

For the sample input above, the output should be:

4

sample

1 10

4