#include <bits/stdc++.h>
using namespace std;
int main(){
  int L, R;
  cin >> L >> R;
  vector<int> g(R + 1, -1);
  int cnt = 0;
  for (int i = L; i <= R; i++){
    if (g[i] == -1){
      g[i] = cnt;
      queue<int> Q;
      Q.push(i);
      while (!Q.empty()){
        int x = Q.front();
        Q.pop();
        for (int j = x * 2; j <= R; j += x){
          if (g[j] == -1){
            g[j] = cnt;
            Q.push(j);
          }
        }
        for (int j = 1; j * j <= x; j++){
          if (x % j == 0){
            if (L <= j && j < x){
              if (g[j] == -1){
                g[j] = cnt;
                Q.push(j);
              }
            }
            int k = x / j;
            if (L <= k && k < x){
              if (g[k] == -1){
                g[k] = cnt;
                Q.push(k);
              }
            }
          }
        }
      }
      cnt++;
    }
  }
  cout << cnt - 1 << endl;
}