#include <iostream>
#include <vector>

using namespace std;
typedef long long int64;

bool contains(int l, int r, int nr) {
	return (l <= nr && nr <= r);
}

vector<int> spec{2, 3, 5, 7, 23, 53, 37, 73};

int main() {
	int a, b;
	cin >> a >> b;

	int ans = 0;
	for (auto el : spec) {
		// cout << el << " " << a << " " << b << "\n";
		if (contains(a, b, el))
			++ans;
	}

	cout << ans << "\n";
}