#include<bits/stdc++.h>
using namespace std;  
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define rep(i,n) for(ll i=0;i<(n);i++)  
#define pii pair<int,int>
#define piii pair<int,pii>
#define mp make_pair
#define pb push_back  
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second  
const int INF = (INT_MAX/2);
const ll LLINF = (LLONG_MAX/2);
const double eps = 1e-5;
const double PI = M_PI;  
#define DEB cout<<"!"<<endl
#define SHOW(a,b) cout<<(a)<<" "<<(b)<<endl
#define SHOWARRAY(ar,i,j) REP(a,i)REP(b,j)cout<<ar[a][b]<<((b==j-1)?((a==i-1)?("\n\n"):("\n")):(" "))
  
#define DIV 1000000007
typedef vector<ll> Array;
typedef vector<Array> matrix;

vi v;

int h(int a){
  if(a /10 == 0) return a;
  int now = 0;
  for(int i = 100000; i != 0; i/=10)
    now += a/i, a -= a/i * i;
  return h(now);
}

bool col(int l,int r){
  map<int,int> m;
  for(int i = l; i <= r && i < v.size(); i++){
    if(!m[v[i]])
      m[v[i]]++;
    else
      return true;
  }
  return false;
}

vi p;

int main(){
  int k,n; cin >> k >> n;
  for(int i = k; i <= n; i++){
    for(int j = 2; j <= i; j++){
      if(j == i-1 || i==2){
        v.pb(h(i));
        p.pb(i);
        break;
      }
      if(i%j==0)
        break;
    }
  }
  int ans = 0;
  int tans = 0;
  int num = 0;
  int l = 0,r = 0;
  while(r != v.size()){
    if(!col(l,r)){
      r++; tans++; if(tans >= ans) num = p[l];
      ans = max(ans,tans);
    }else{
      tans--;l++;
    }
  }
  cout << num << endl;
}