#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <tuple>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <ranges>
using namespace std;
using ll = long long;

auto range(int n) { return views::iota(0, n); }

template<class T, class U> ostream& operator<<(ostream& os, const pair<T, U>& p){ return os << "{" << p.first << ", " << p.second << "}"; }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& obj) { os << "{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T> ostream& operator<<(ostream& os, const set<T>& obj) { os << "set{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& obj) { os << "map{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }

#ifdef ONLINE_JUDGE
#define dump(expr) ;
#else
#define dump(expr) { cerr << "\033[33m#L" << __LINE__ << ": " << expr << "\033[39m" << endl; }
#endif

struct UF {
  vector<int> data;
  void init(int n) { data = vector<int>(n, -1); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  bool find(int x, int y) { return root(x) == root(y); }
  void uni(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[x] < data[y])
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
    }
  }
};

int solve() {
  int n, m; cin >> n >> m;
  if (n == 1) return 0;
  // dump(dbg(n, m));

  UF uf;
  uf.init(m + 1);

  for (int i = n; i <= m; ++i) {
    for (int j = 2 * i; j <= m; j += i) uf.uni(i, j);
  }
  int res = 0;
  for (int i = n; i <= m; ++i) res += uf.root(i) == i;
  return res - 1;
}

int main() {
  cout << solve() << endl;
}