#include<iostream>
#include<cstdio> 
#include<string>
#include<algorithm>
using namespace std;
int a,b,d;
char c[10];
bool Fun_SS(int h){
	for(int i=2;i*i<=h;++i){
		if(h%i==0)
			return 0;
	}
	return 1;
}
bool Fun_HW(int e,string n){
	if(n.size()==1){
		if(Fun_SS(e)) return 1;
		else return 0;
	}
	string s;
	s=n;
	int u=s.size();
	reverse(s.begin(),s.end());
	if(s==n){
		if(Fun_SS(e)==1) return 1;
		else return 0;
	}
	else return 0;
}
int main(){
	cin>>a>>b;
	if(a%2==0)
		a++;
	for(int i=a;i<=b;i=i+2){
		sprintf(c,"%d",i);
		string l=c;
		if(Fun_HW(i,l))cout<<i<<endl;
	}
	return 0;
}