//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 100010001;
const ll LINF = (ll)INF*INF*10;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

const size_t N = 2e5+10;

struct UnionFind {
  vector<int> par; // 親を指すvector,-par[親]は木のサイズ
  UnionFind(int n):par(n, -1) {} // uniteで親を埋め込んでいく必要あり
  int root(int x) { // 親をたどる&データの整理
    if(par[x] < 0) return x;
    return par[x] = root(par[x]);
  }
  bool unite(int x, int y) { // データの結合
    x = root(x);
    y = root(y);
    if(x == y) return false;
    if(par[x] > par[y]) swap(x, y);
    par[x] += par[y];
    par[y] = x;
    return true;
  }
  bool same(int x, int y) {return root(x) == root(y);} // 所属判定
  int size(int x) {return -par[root(x)];} // 木のサイズ
};

//head

int l, r;
int ans = -1;
UnionFind uft(N);

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> l >> r;
  for(int i = l; i <= r; i++) {
    if(i*2 <= r) for(int j = i*2; j <= r; j += i) {
      uft.unite(i, j);
    }
  }

  for(int i = l; i <= r; i++) if(i == uft.root(i)) ans++;

  cout << ans << endl;
}