#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<i64>();
    let (l, r) = (v[0], v[1]);
    let primes = get_primes(100000);
    // debug!(primes.len());
    let mut squares = primes.iter().map(|&x| x * x).collect::<Vec<_>>();
    let mut divided = vec![false; (r - l + 1) as usize];
    for &p in &squares {
        let mut cur = l / p * p;
        while cur <= r {
            if cur >= l {
                divided[(cur - l) as usize] = true;
            }
            cur += p;
        }
    }
    let ans = divided.iter().filter(|&&x| !x).count();
    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

fn get_primes(n: i64) -> Vec<i64> {
    let mut is_prime = vec![true; n as usize + 1];
    let mut primes = Vec::new();
    is_prime[0] = false;
    is_prime[1] = false;

    for i in 2..n + 1 {
        if is_prime[i as usize] {
            primes.push(i);
            let mut j = 2 * i;
            while j <= n {
                is_prime[j as usize] = false;
                j += i;
            }
        }
    }
    primes
}