#include <bits/stdc++.h>

using namespace std;

int a,b,ans;
int cifrepare[]={2,3,5,7,23,37,73,53};
int main(){
    scanf("%d%d",&a,&b);
    if (a<=cifrepare[0]&&cifrepare[0]<=b){
        ans++;
    }
    if (a<=cifrepare[1]&&cifrepare[1]<=b){
        ans++;
    }
    if (a<=cifrepare[2]&&cifrepare[2]<=b){
        ans++;
    }
    if (a<=cifrepare[3]&&cifrepare[3]<=b){
        ans++;
    }
    if (a<=cifrepare[4]&&cifrepare[4]<=b){
        ans++;
    }
    if (a<=cifrepare[5]&&cifrepare[5]<=b){
        ans++;
    }
    if (a<=cifrepare[6]&&cifrepare[6]<=b){
        ans++;
    }
    if (a<=cifrepare[7]&&cifrepare[7]<=b){
        ans++;
    }

    cout<<ans;
}