#define _CRT_SECURE_NO_WARNINGS
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#include <stack>
#include <array>
#include <fstream>
#include <deque>
#include <bitset>


#define REP(i,n) for(int (i) = 0;(i) < (n) ; ++(i))
#define REPS(a,i,n) for(int (i) = (a) ; (i) < (n) ; ++(i))
#if defined(_MSC_VER)||__cplusplus > 199711L
#define AUTO(r,v) auto r = (v)
#else
#define AUTO(r,v) typeof(v) r = (v)
#endif
#define ALL(c) (c).begin() , (c).end()
#define EACH(it,c) for(AUTO(it,(c).begin());it != (c).end();++it)
#define LL long long
#define int LL
#define INF  99999999
#define DIV 1000000007
#define QUICK_CIN ios::sync_with_stdio(false); cin.tie(0);
#define InitArr1(c,n) memset(&c[0],0,sizeof(int)*n)
#define InitArr2(c,n) memset(&c[0][0],0,sizeof(int)*n)

template<class T>
bool valid(T x, T w) { return 0 <= x&&x < w; }

int di[4] = { 1, -1, 0, 0 };
int dj[4] = { 0, 0, 1, -1 };

using namespace std;

//-----------------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------------------------


int k, n;

signed main()
{
	QUICK_CIN;


		while (cin >> k >> n) {
			bool prime[210000];
			REP(i, 210000)
				prime[i] = false;


			for (int i = 2; i < 210000; ++i) {
				for (int j = i * 2; j < 210000; j += i) {
					prime[j] = true;
				}
			}

			vector<int> primes(0);
			vector<int> val(0);

			REP(i, 209999) {
				if (!prime[i + 1])
					primes.push_back(i + 1);
			}

			for (auto x : primes) {
				int s = 0;
				int z = 0;
				do {
					while (x) {
						s += x % 10;
						x /= 10;
					}
					x = s;
					z = s;
					s = 0;
				} while (z > 9);

				val.push_back(z);
			}
			bool buf[10];
			REP(i, 10) {
				buf[i] = false;
			}
			int si(-1), gi(-1);

			while (k > primes[++si]);
			while (n >= primes[++gi]);
			gi--;

			int max_i = si;
			int max_v = 0;
			int v = 0;

			int i = si;
			int j = si;

			while (j <= gi && i <= j) {
				while (!buf[val[j]]) {
					buf[val[j]] = true;
					++v;
					++j;

					if (v >= max_v) {
						max_v = v;
						max_i = i;
					}
				}
				while (buf[val[j]]) {
					buf[val[i]] = false;
					++i;
					--v;
				}
			}

			cout << primes[max_i] << endl;
		}

}