#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

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

#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

const double EPS = 1e-10;
const double PI  = acos(-1.0);

#define CLR(a) memset((a), 0 ,sizeof(a))

#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int K, N;
	cin >> K >> N;

	vector<int> prime;
	vector<bool> isPrime(N + 1, true);
	FOR(i, 2, N + 1){
		if(isPrime[i]){
			if(i >= K) prime.push_back(i);
			for(auto j = 2 * i; j < N + 1; j += i){
				isPrime[j] = false;
			}
		}
	}

	function<int(int)> h = [&](int num){
		int ret = 0, tmp = 1;
		while(tmp < num) tmp *= 10;
		while(num != 0){
			ret += num / tmp;
			num -= num / tmp * tmp;
			tmp /= 10;
		}
		if(ret >= 10) ret = h(ret);
		return ret;
	};

	int ret = prime[0], num = 0;
	for(auto i: prime){
		vector<bool> exist(10, false);
		int cnt = 0;
		for(auto j: prime){
			if(j >= i){
				//cout << i << " " << j << " " << h(j) <<  endl;
				if(exist[h(j)]) break;
				cnt++;
				exist[h(j)] = true;
			}
		}
		//cout << i << " " << cnt << endl;
		if(cnt >= num){
			num = cnt;
			ret = i;
		}
	}

	cout << ret << endl;

	return 0;
}