struct UnionFind {
    n: usize,
    parents: Vec<usize>,
}

impl UnionFind {
    fn new(n: usize) -> Self {
        UnionFind {
            n: n,
            parents: (0..n).collect(),
        }
    }

    fn equiv(&mut self, a: usize, b: usize) -> bool {
        self.find(a) == self.find(b)
    }
    
    fn unite(&mut self, a: usize, b: usize) {
        if self.equiv(a, b) { return; }
        let (a, b) = (a.min(b), a.max(b));
        let x = self.parents[a];
        let y = self.parents[b];
        self.parents[y] = self.parents[x];
    }

    fn find(&mut self, a: usize) -> usize {
        if self.parents[a] == a { return a; }
        let p = self.find(self.parents[a]);
        self.parents[a] = p;
        p
    }
}

fn main() {
    let mut lr = String::new();
    std::io::stdin().read_line(&mut lr).ok();
    let lr: Vec<usize> = lr.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let l = lr[0];
    let r = lr[1];

    let mut uf = UnionFind::new(r + 10);
    for i in l..r {
        for j in 2..1000000 {
            let val = i * j;
            if val > r { break; }
            uf.unite(i, val);
        }
    }
    let mut result = 0usize;
    for i in l..r {
        if uf.find(i) != uf.find(i+1) {
            result += 1;
            uf.unite(i, i+1);
        }
    }
    println!("{}", result);
}