#define REP(i,n) for(int i=0; i<(int)(n); i++)

#include <queue>
#include <cstdio>
inline int getInt(){ int s; scanf("%d", &s); return s; }

#include <set>

using namespace std;

int main(){
  const int k = getInt();
  const int n = getInt();

  vector<int> p;
  vector<int> h;

  for(int i = max(2, k); i <= n; i++){
    bool ok = true;
    for(int j = 2; j * j <= i; j++)
      if(i % j == 0){ ok = false; break; }
    if(!ok) continue;
    p.push_back(i);
    int hh = i;
    while(hh >= 10){
      int t = 0;
      while(hh){ t += hh % 10; hh /= 10; }
      hh = t;
    }
    h.push_back(hh);
  }

  int len = 0;
  int ans = 0;

  int fst = 0;

  set<int> s;
  REP(i,p.size()){
    if(s.count(h[i])){
      do{
        s.erase(h[fst]);
      }while(h[fst++] != h[i]);
    }
    s.insert(h[i]);
    // printf("%d(%d): %d\n", p[i], h[i], p[fst]);
    if(len <= i - fst + 1){
      len = i - fst + 1;
      ans = p[fst];
    }
  }

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

  return 0;
}