#include<iostream>
#include<algorithm>
#include<cstring>
#include <vector>
#include <cmath>

using namespace std;
const int N = 10000000;//八位数都不用枚举

int a,b;
bool isprime(int x)//简单的判断质数的函数
{
    if(x <= 1) return false;
    if(x == 2) return true;
    if(x % 2 == 0) return false;
    for(int i = 3;i <= sqrt(x);i += 2)
    if(x % i == 0) return false;
    return true;
}
bool iswen(int num)//判断回文数
{
    int ori = num;
    int rev = 0;
    while (num > 0) {
        rev = rev * 10 + num % 10;
        num /= 10;
    }
    return ori == rev;
}
int main() 
{
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);

    cin>>a>>b;

    b=min(b,N);//八位数不用枚举

    for(int i=a;i<=b;i++)
    if(iswen(i)&&isprime(i))//都满足则输出
    cout<<i<<endl;

    return 0;
}