#include <iostream>
#include <vector>
#include <cassert> 

using namespace std ;

/*ifstream cin ("input") ;
ofstream cout ("output") ;*/

int cif [] = {2,3,5,7} ;

bool isPrime (long long n) {
	if (n == 1) return false ;
	if (n == 2) return true ;
	if (n == 3) return true ;
	long long d = 2 ; 
	while (d * d <= n) {
		if (n % d == 0) {
			return false ;
		}
		d += 1 ;
	}
	return true ;
}
vector <long long> sol ;
void compute (long long cur) {
	if (cur > (long long)(1e9)) {
		return ; 
	}
	if (isPrime(cur)) {
		sol.push_back(cur) ;
		for (int i = 0 ; i < 4 ; ++ i) {
			compute (cur * 10 + cif[i]) ;
		}
	}
}

int main(int argc, char const *argv[])
{
	compute(0) ;
	int a , b ; 
	cin >> a >> b ;
	assert (a >= 1 and b >= 1) ;
	int ans = 0 ; 
	for (auto x : sol) {
		if (x >= a and x <= b) {
			ans += 1 ; 
		}
	}
	cout << ans << '\n' ;
	return 0;
}