#include <iostream>

#include <cstdio>

#include <string.h>

#include <cmath>

using namespace std;

const int maxn=;

typedef long long LL;

int numPrime[maxn],numpalindrome[maxn];

void sieve()

{

    int na=*;

    int m=sqrt(na+);

    for(LL i=; i<=m; i++)if(numPrime[i]){

       for(LL j=i*i; j<=na; j+=i) numPrime[j]=;

    }

}

int a[];

int jud(int n)

{

    int t=n,m=;

    while(t)

        m=m*+t%,t/=;

    return n==m;

}

int main()

{

   for(int i=; i<maxn; i++)numPrime[i]=;

   sieve();

   for(int i=; i<maxn; i++)numPrime[i]+=numPrime[i-];

   for(int i=; i<maxn; i++)numpalindrome[i]+=jud(i)+numpalindrome[i-];

   int p,q;

   while(scanf("%d%d",&p,&q)==)

    {

          int ans=-;

           for(int i=; i<=; i++)

            if(numPrime[i]*q<=numpalindrome[i]*p)ans=i;

            if(ans==-) puts("Palindromic tree is better than splay tree");

            else printf("%d\n",ans);

    }

    return ;

}