#include<bits/stdc++.h>
#define pb push_back
using namespace std; 
typedef long long ll;
ll N,a,b,rs;
bool P[100];
int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    P[2] = P[3] = P[5] = P[7] = P[23] = P[37] = P[53] = P[73]= 1;
    cin >> a >> b;
    for(int i = a;i<=b && i<=100;i++) rs+=P[i];
    cout << rs;
}