// mc4a.cpp : Defines the entry point for the console application.
//

#include <iostream>
#include <vector>
using namespace std;
int sir[10] = { 2, 3, 5, 7, 23, 37, 53 };
bool visited[10];

int main()
{
    int a, b;
    cin >> a >> b;
    int cnt = 0;
    for (int i = 0; i < 7; i++)
    {
        if (a <= sir[i] && b >= sir[i])
            cnt++;
    }
    cout << cnt;
}