#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
#define INF (1<<30)
#define INFLL (1ll<<60)
typedef pair<int, int> P;
typedef pair<int, P> E;
#define MOD (1000000007ll)
#define l_ength size
#define EPS (1e-10)

void add_mod(ll &a, ll b){
	a += b;
	a %= MOD;
}

void mul_mod(ll &a, ll b){
	a *= b;
	a %= MOD;
}

int f(int x){
	return (x<10)?x:x%10+f(x/10);
}

bool isp[225816];
vector<P> v;

int main(void){
	int k,n,i,j,p,m,t,ans,memo=0;
	bool d[10];
	fill(isp,isp+225816,true);
	isp[1] = false;
	cin >> k >> n;
	for(i=2; i<=500; ++i){
		if(!isp[i]){
			continue;
		}
		for(j=i*2; j<=n; j+=i){
			isp[j] = false;
		}
	}
	for(i=k; i<=n; ++i){
		if(!isp[i]){
			continue;
		}
		p = i;
		while(p>9){
			p = f(p);
		}
		v.push_back(P(p,i));
	}
	m = v.l_ength();
	for(i=0; i<m; ++i){
		fill(d,d+10,false);
		t = min(m,i+10)-i;
		for(j=i; j<min(m,i+10); ++j){
			if(d[v[j].first]){
				t = j-i;
				break;
			}else{
				d[v[j].first] = true;
			}
		}
		if(memo <= t){
			ans = v[i].second;
			memo = t;
		}
	}
	cout << ans << endl;
	return 0;
}