#include <bits/stdc++.h>
using namespace std;

#define REP(i,a) for (int i = 0; i < a; i++)
#define FOR(i,a,b) for (int i = a; i <= b; i++)
#define ROF(i,a,b) for (int i = a; i >= b; i--)
#define FOREACH(it,x) for (__typeof((x).begin()) it = (x).begin(); it != (x).end(); it++)
#define all(x) (x).begin(),(x).end()
#define UNIQUE(x) sort(all(x)),(x).erase(unique(all(x)),(x).end())
#define ll long long
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define pii pair<int,int>
#define SZ(x) ((int)(x).size())

const int primes[] = {2,3,5,7,23,37,53,73};

int main()
{
    ios_base::sync_with_stdio(false);
    int a,b; cin >> a >> b;
    int sum = 0; REP(i,8) if (primes[i] >= a && primes[i] <= b) sum++;
    cout << sum;
}