/*
TASK:rprimes
LANG:C++
*/

#include <iostream>
#include <math.h>
using namespace std;

bool prime (int l) {
	int i,j=sqrt(l);
	if (l==1) return false;
	for (i=2;i<=j;i++) {
		if (l%i==0) return false;
	}
	return true;
}

bool rprime (int k) {
	if (k/10==0) return prime(k);
	return (prime(k) && rprime(k/10));
}

int main () {
	int s=0,a,b;
	cin >> a >> b;
	int h;
	for (h=a;h<=b;h++) {
		if (rprime(h)) {
			s++;
		}
	}
	cout << s << endl;
	return 0;
}
