#include <bits/stdc++.h>
using namespace std;
bool ktra1(long long n) {
    if (n<2) return false;
    for (long long i=2;i*i<=n;++i)
        if (n%i==0) return false;
    return true;
}
bool ktra2(long long n) {
    long long r=0,tam=n;
    while (tam) {
        r=r*10+tam%10;
        tam/=10;
    }
    return r==n;
}
int main() {
    long long a,b,dem=0;
    //freopen("SODEP.INP","r",stdin);
    //freopen("SODEP.OUT","w",stdout);
    cin>>a>>b;
    for (long long i=ceil(sqrt(a));i<=floor(sqrt(b));++i) {
        long long kq=i*i;
        if (kq>=a && kq<=b && ktra2(kq) && ktra1(i))
            dem++;
    }
    cout<<dem;
    return 0;
}