#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = (ll)(1e+9) + 7;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
typedef pair<ld, ld> LDP;
int k, n;
bool isp[1 << 18];
vector<int> p;
void init() {
	fill(isp + 2, isp + (1 << 18),true);
	Rep(i, 2, (1 << 18)) {
		if (!isp[i])continue;
		if (k <= i && i <= n)p.push_back(i);
		for (int j = 2 * i; j < (1<<18); j += i) {
			isp[j] = false;
		}
	}
}
int calc(int x) {
	int c = x; int s = 0;
	while (c) {
		s += c % 10; c /= 10;
	}
	if (s < 10)return s;
	else return calc(s);
}
int used[10];
int main(){
	cin >> k >> n; init();
	int m = p.size();
	int ma = 0; int out = 0;
	int le = 0;
	rep(i, m) {
		int t = calc(p[i]);
		if (used[t]) {
			while (t != calc(p[le])) {
				used[calc(p[le])] = false;
				le++;
			}
			le++;
		}
		used[t] = true;
		if (ma <= i - le + 1) {
			ma = i - le + 1;
			out = p[le];
		}
	}
	cout << out << endl;
	return 0;
}