#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<int,int>;
#define sr string 
#define vc vector
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
  int l,r;cin>>l>>r;
  dsu d(r+1);
  for(int i=l;i<=r;i++)for(int j=2*i;j<=r;j+=i)d.merge(i,j);
  int ans=-1;
  for(int i=l;i<=r;i++)if(d.leader(i)==i)ans++;
  cout<<ans;
}