#include <cstdio>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <string>
#include <string.h>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <map>
#include <set>
#include <iostream>
#include <sstream>
#include <cctype>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rrep(i,n) for(int i = 1; i <= n; ++i)
#define drep(i,n) for(int i = n-1; i >= 0; --i)
#define gep(i,g,j) for(int i = g.head[j]; i != -1; i = g.e[i].next)
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcount
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
inline int in() { int x; scanf("%d",&x); return x;}
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;

const int MX = 200005, INF = 1000010000;
const ll LINF = 1000000000000000000ll;
const double eps = 1e-10;
const int di[] = {-1,0,1,0}, dj[] = {0,-1,0,1}; //^<v>

int f(int x) {
  if (x < 10) return x;
  int a = 0;
  while (x) {
    a += x%10;
    x /= 10;
  }
  return f(a);
}

int d[MX];

// Eratosthenes' sieve
vector<int> ps; vector<bool> pf;
void sieve(int mx){
	pf.resize(mx+1); fill(rng(pf),true); pf[0] = pf[1] = false;
	for(ll i = 2; i <= mx; i++){
		if(!pf[i]) continue;
		ps.pb(i);
		for(ll j = i*i; j <= mx; j+=i) pf[j] = false;
	}
}
//

int main(){
  int n, k;
  cin >> k >> n;
  sieve(MX);
  vi e;
  for (int i = k; i <= n; ++i) if (pf[i]) e.pb(i);
  n = e.size();
  rep(i,n) d[i] = f(e[i]);
  //rep(i,n) printf("%d\n",d[i]);
  P ans(0,0);
  rep(i,n) {
    int c = 0;
    vi s(10);
    rep(j,10) {
      int a = i+j;
      if (a > n || s[d[a]]) break;
      s[d[a]] = 1;
      c++;
    }
    ans = max(ans,{c,e[i]});
  }
  cout << ans.se << endl;
  return 0;
}