#include<bits/stdc++.h>
using namespace std;
int p[100] ={2,3,5,7,23,37,53,73};
int a,b;
int main()
{
	cin >> a >> b;
	int rez =0;
	for(int i = 0; i < 8; i++) if(p[i] >= a && p[i] <= b) rez++;
	cout << rez;
}