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

int main(){
  long long int K,N;
  cin >> K >> N;
  vector<long long int> P(0);
  for(long long int i=K;i<=N;i++){
    if(i == 1) continue;
    bool flag = true;
    for(long long int j=2;j*j<=i;j++){
      if(i%j == 0){
        flag = false;
        break;
      }
    }
    if(flag) P.push_back(i);
  }
  vector<long long int> A(P.size());
  for(int i=0;i<P.size();i++){
    A[i] = P[i];
    while(A[i] >= 10){
      long long int S = 0;
      while(A[i] > 0){
        S += A[i]%10;
        A[i] /= 10;
      }
      A[i] = S;
    }
  }
  for(int i=9;i>=1;i--){
    int ans = -1;
    for(int j=0;j<(int)P.size()-i+1;j++){
      vector<bool> used(10,false);
      bool ok = true;
      for(int k=j;k<j+i;k++){
        if(used[A[k]]){
          ok = false;
          break;
        }
        else used[A[k]] = true;
      }
      if(ok) ans = P[j];
    }
    if(ans != -1){
      cout << ans << endl;
      break;
    }
  }
}