#include <iostream>
#include <string>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>
#include <assert.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef pair<ll,ll> P;
typedef vector<P> vpl;
typedef tuple<ll,ll,ll> tapu;
#define rep(i,n) for(ll i=0; i<(n); i++)
#define REP(i,a,b) for(int i=(a); i<(b); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int inf = 1<<30;
const ll linf = 1LL<<62;
const int MAX = 510000;
ll dy[8] = {1,-1,0,0,1,-1,1,-1};
ll dx[8] = {0,0,1,-1,1,-1,-1,1};
const double pi = acos(-1);
const double eps = 1e-7;
template<typename T1,typename T2> inline bool chmin(T1 &a,T2 b){
	if(a>b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline bool chmax(T1 &a,T2 b){
	if(a<b){
		a = b; return true;
	}
	else return false;
}
template<typename T> inline void print(T &a){
    rep(i,a.size()) cout << a[i] << " ";
    cout << "\n";
}
template<typename T1,typename T2> inline void print2(T1 a, T2 b){cout << a << " " << b << "\n";}
template<typename T1,typename T2,typename T3> inline void print3(T1 a, T2 b, T3 c){
	cout << a << " " << b << " " << c << "\n";
}
const int mod = 1e9 + 7;
//const int mod = 998244353;

struct UnionFind{
    vl p;
    vl rank;
    vl cnt;

    UnionFind(ll n){
        rank.resize(n,0);
        p.resize(n,0);
        cnt.resize(n,0);
        rep(i,n){
            p[i] = i;
            rank[i] = 0;
            cnt[i] = 1;
        }
    }

    ll find(ll x){
        if(x != p[x]) p[x] = find(p[x]);
        return p[x];
    }

    bool same(ll x, ll y){
        return find(x) == find(y);
    }

    void unite(ll x, ll y){
        x = find(x);
        y = find(y);
        if(x == y) return;
        if(rank[x] > rank[y]){
            p[y] = x;
            cnt[x] += cnt[y];
        }else{
            p[x] = y;
            cnt[y] += cnt[x];
            if(rank[x] == rank[y]) rank[y]++;
        }
    }

    ll size(ll x){
        return cnt[find(x)];
    }
};

int main(){
    ll l,r; cin >> l >> r;
    UnionFind uf(r-l+1);
    for(ll i=l; i<=r; i++){
        for(ll j=i+i; j<=r; j+=i){
            uf.unite(i-l,j-l);
        }
    }
    ll ans = 0;
    for(ll i=l; i<r; i++){
        if(!uf.same(i-l,i-l+1)){
            uf.unite(i-l,i-l+1);
            ans++;
        }
    }
    cout << ans << endl;
}