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

int reverseInt(int x){
    int ans=0;
    while(x!=0){
        ans*=10;
        ans+=x%10;
        x/=10;
    }
    return ans;
}

int main() {
    int a,b;
    while(cin>>a>>b){
        vector<int>primePass(b+1);
        map<int,int>mp;
        for(int i=2;i*i<=b;i++){
            int l=2;
            while(i*l<=b){
                primePass[i*l]=1;
                l++;
            }
        }
        for(int i=2;i<=b;i++){
            if(primePass[i]==0)mp[i]++;
        }
        for(int i=a;i<=b;i++){
            if(mp[i]==1){
                if(reverseInt(i)==i)cout<<i<<endl;
            }
        }
    }
}