#include <iostream>
#include <vector>
#include <map>
#define Nmax 100000
using namespace std;
int a,b,s;
int main()
{
    cin>>a>>b;
   if(2>=a && 2<=b)s++;
   if(3>=a && 3<=b)s++;
   if(5>=a && 5<=b)s++;
   if(7>=a && 7<=b)s++;
   if(23>=a && 23<=b)s++;
   if(37>=a && 37<=b)s++;
   if(53>=a && 53<=b)s++;
   if(73>=a && 73<=b)s++;
   cout<<s;
    return 0;
}