https://www.e-olymp.com/az/problems/33

/*
    Author: Kanan Asgarli
    https://www.e-olymp.com/az/problems/33
*/
#include <iostream>
#include <cmath>
#define MAX 500000
using namespace std;
int primes[MAX+1], a, b, say;
void gen_primes(){
    primes[1] = 1;
    for(int i = 2; i <= sqrt(MAX); i++){
        if(primes[i] == 0)
            for(int j = i*i; j <= MAX; j += i)
                primes[j] = 1;
    }
}
bool check(int n){
    int d = n%10;
    while(n > 0){
        if(d == 3 && n%10 == 1)
            return false;
        else{
            d = n%10;
            n = n/10;
        }
    }
    return true;
}
int main()
{
   cin>>a>>b;
   if(a > b)
       swap(a,b);
   gen_primes();
   for(int i = a; i <= b; i++){
        if(primes[i] == 0 && check(i) == true)
            say++;
    }
   cout<<say<<endl;

   return 0;
}