#include <bits/stdc++.h>

#define pb push_back
#define f first
#define s second
#define pii pair<int, int>
#define mp make_pair
 
using namespace std;
 
const string name = "A",
             in_file = name + ".in",
             out_file = name + ".out";
 
ifstream fin(in_file);
ofstream fout(out_file);
 
int valid[] = {2, 3, 5, 7, 23, 37, 53, 73};

int main() {
	int a, b;
	cin >> a >> b;
	int count = 0;
	for (int i = 0; i < 8; i++) {
		if (valid[i] >= a && valid[i] <= b) {
			count++;
		}
	}
	cout << count;
	return 0;
}