#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

struct UnionFind {
  UnionFind(int n) : data(n, -1) {}

  int root(int ver) { return data[ver] < 0 ? ver : data[ver] = root(data[ver]); }

  bool unite(int u, int v) {
    u = root(u);
    v = root(v);
    if (u == v) return false;
    if (data[u] > data[v]) swap(u, v);
    data[u] += data[v];
    data[v] = u;
    return true;
  }

  bool same(int u, int v) { return root(u) == root(v); }

  int size(int ver) { return -data[root(ver)]; }

private:
  vector<int> data;
};

int main() {
  int l, r; cin >> l >> r;
  UnionFind uf(r + 1);
  FOR(i, l, r + 1) {
    for (int j = i + i; j <= r; j += i) uf.unite(i, j);
  }
  set<int> st;
  FOR(i, l, r + 1) st.emplace(uf.root(i));
  cout << st.size() - 1 << '\n';
  return 0;
}