#include <iostream>
#include <fstream>
using namespace std;
int a, b, v[20] = {2,3,5,7,23,37,73,53}, rez;

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