#include <algorithm>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

vector<bool> sieve(int x) { // range...[0,x]
    vector<bool> flags(x + 1, true);
    flags[0] = false, flags[1] = false;
    for(int i = 2; i * i <= x; i++) {
        if(!flags[i])
            continue;
        for(int mult = i * i; mult < x; mult += i)
            flags[mult] = false;
    }
    return flags;
}

ll getLdiv(ll n) {
    for(ll i = 2; i * i <= n; i++) {
        if(n % i == 0) {
            return n / i;
        }
    }
    return 1;
}

// UnionFind
struct UnionFind {
    vector<ll> par;
    vector<ll> siz;

    UnionFind(ll N) : par(N), siz(N, 1LL) {
        for(int i = 0; i < N; i++)
            par[i] = i;
    }
    int root(int x) {
        if(par[x] == x)
            return x;
        return par[x] = root(par[x]);
    }
    void unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if(rx == ry)
            return;
        if(siz[rx] < siz[ry])
            swap(rx, ry);
        siz[rx] += siz[ry];
        par[ry] = rx;
    }
    bool same(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }
    ll size(ll x) { return siz[root(x)]; }
};

int main() {
    int L, R;
    cin >> L >> R;
    vector<bool> A(200001, 1);
    vector<bool> is_prime = sieve(200001);
    if(L == 1) {
        cout << 0 << endl;
        return 0;
    }
    UnionFind uf(R - L + 1);
    for(int i = L; i <= R; i++) {
        for(int j = i * 2; j <= R; j += i) {
            uf.unite(i - L, j - L);
        }
    }
    set<int> se;
    for(int i = L; i <= R; i++) {
        se.insert(uf.root(i - L));
    }
    cout << se.size() - 1 << endl;
    return 0;
}