#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <cstring>
#include <map>
#include <iomanip>
#include <cstdio>
#define mp make_pair
#define pb push_back
#define LL long long
#define inf 2e9
#define zeros x^(x-1)&x
using namespace std;

int pd[] = {2,3,5,7,23,37,53},a,b;


int main()
{
    //bkt(1,0);
    int nr= 0;
    cin>>a>>b;
    for (int i=0;i<7;i++)
        if (a<=pd[i] && pd[i]<=b)
            nr++;
    cout<<nr;
    return 0;
}