#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0);
#define tie cin.tie(0);
  
using namespace std;
template < class T > T emin(T &a,T b) {if (a > b) a = b;return a;}
template < class T > T emax(T &a,T b) {if (a < b) a = b;return a;}

int a, b, nr;
const int n[] = {2, 3, 5, 7, 23, 37, 53, 73};

int main(){
    IOS tie
    cin >> a >> b;
    for (int i = a; i <= b; i++)
    {
        if (i > 73) break;
        for (int j = 0; j < 8; j++) if (i == n[j]) nr++;
    }
    cout << nr;
}