//#define NDEBUG
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <utility>
#include <vector>

namespace n91 {

using i8 = std::int_fast8_t;
using i32 = std::int_fast32_t;
using i64 = std::int_fast64_t;
using u8 = std::uint_fast8_t;
using u32 = std::uint_fast32_t;
using u64 = std::uint_fast64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

struct rep {
  struct itr {
    usize i;
    constexpr itr(const usize i) noexcept : i(i) {}
    void operator++() noexcept { ++i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  const itr f, l;
  constexpr rep(const usize f, const usize l) noexcept
      : f(std::min(f, l)), l(l) {}
  constexpr auto begin() const noexcept { return f; }
  constexpr auto end() const noexcept { return l; }
};
struct revrep {
  struct itr {
    usize i;
    constexpr itr(const usize i) noexcept : i(i) {}
    void operator++() noexcept { --i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  const itr f, l;
  constexpr revrep(const usize f, const usize l) noexcept
      : f(l - 1), l(std::min(f, l) - 1) {}
  constexpr auto begin() const noexcept { return f; }
  constexpr auto end() const noexcept { return l; }
};
template <class T> auto md_vec(const usize n, const T &value) {
  return std::vector<T>(n, value);
}
template <class... Args> auto md_vec(const usize n, Args... args) {
  return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> constexpr T difference(const T &a, const T &b) noexcept {
  return a < b ? b - a : a - b;
}
template <class T> void chmin(T &a, const T &b) noexcept {
  if (b < a)
    a = b;
}
template <class T> void chmax(T &a, const T &b) noexcept {
  if (a < b)
    a = b;
}
template <class F> class rec_lambda {
  F f;

public:
  rec_lambda(F &&f) : f(std::move(f)) {}
  template <class... Args> auto operator()(Args &&... args) const {
    return f(*this, std::forward<Args>(args)...);
  }
};
template <class F> auto make_rec(F &&f) { return rec_lambda<F>(std::move(f)); }
template <class T> T scan() {
  T ret;
  std::cin >> ret;
  return ret;
}
constexpr char eoln = '\n';
template <class T> T ceildiv(const T &l, const T &r) {
  return l / r + (l % r != 0 ? 1 : 0);
}

} // namespace n91

namespace n91 {

#include <cassert>
#include <utility>
#include <vector>

class union_find {
private:
  class node_type {
    friend union_find;

    usize parent;
    usize size;

    node_type(const usize parent, const usize size)
        : parent(parent), size(size) {}
  };

  std::vector<node_type> tree;

public:
  union_find() = default;

  explicit union_find(const usize n) : tree(n, node_type(n, 1)) {}

  usize size() const { return tree.size(); }

  usize find(const usize x) {
    assert(x < size());
    if (tree[x].parent == size())
      return x;
    else
      return tree[x].parent = find(tree[x].parent);
  }

  bool same(const usize x, const usize y) {
    assert(x < size());
    assert(y < size());
    return find(x) == find(y);
  }

  usize size(const usize x) {
    assert(x < size());
    return tree[find(x)].size;
  }

  void unite(usize x, usize y) {
    assert(x < size());
    assert(y < size());
    x = find(x);
    y = find(y);
    if (x != y) {
      if (tree[x].size < tree[y].size)
        std::swap(x, y);
      tree[x].size += tree[y].size;
      tree[y].parent = x;
    }
  }
};

void main_() {
  /*
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  //*/

  const usize l = scan<usize>();
  const usize r = scan<usize>() + 1;

  union_find uf(r - l);
  usize count = r - l;
  for (const usize i : rep(l, r)) {
    for (usize j = i * 2; j < r; j += i) {
      if (!uf.same(i - l, j - l)) {
        count -= 1;
        uf.unite(i - l, j - l);
      }
    }
  }

  std::cout << count - 1 << eoln;
}

} // namespace n91

int main() {
  n91::main_();
  return 0;
}