#include <bits/stdc++.h>
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); ++i)
#define rep(i, n) REP(i, 0, n)
using namespace std;
using ll = long long;
using ld = long double;
template<class T, class U> inline bool chmax(T &a, const U &b) { if(a < b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if(a > b) { a = b; return true; } return false; }

struct UnionFind {
  vector<int> data;
  UnionFind(int n) : data(n, -1) {}

  int root(int x) {
    if(data[x] < 0) return x;
    return data[x] = root(data[x]);
  }

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

  int same(int x, int y) {
    return root(x) == root(y);
  }

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


int l, r;

int main() {
  cin.tie(0); ios::sync_with_stdio(false);
  cin >> l >> r;
  UnionFind uf(r-l+1);
  REP(i, l, r+1) {
    if(uf.root(i-l) != i-l) continue;
    for(ll j = i*2; j <= r; j += i) {
      uf.unite(i-l, j-l);
    }
  }
  ll ans = 0;
  rep(i, r-l+1) if(uf.root(i) == i) ans++;
  ans--;
  cout << ans << '\n';
  return 0;
}