#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <complex>
#include <string.h>
using namespace std;

#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef pair<int, int> P;
typedef unsigned int uint;

const int inf = 1000000009;

bool is_prime[200010];

vector<int> sieve(int k, int n) {
    vector<int> res;
    memset(is_prime, true, sizeof(is_prime));
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i <= n; i++) {
	if (is_prime[i]) {
	    if (i >= k)
		res.push_back(i);
	    for (int j = i + i; j <= n; j += i)
		is_prime[j] = false;
	}
    }
    return res;
}

int h(int n) {
    if (n < 10) return n;
    int k = 0;
    while (n > 0) {
	k += (n % 10);
	n /= 10;
    }
    return h(k);
}

int solve(int k, int n) {
    vector<int> ps = sieve(k, n);
    vector<int> ori = ps;
    int len = ps.size();
    for (int i = 0; i < len; i++)
	ps[i] = h(ps[i]);

    int res = ori[0], s = 1, maxi = 1;
    bool used[10];
    memset(used, false, sizeof(used));
    used[ps[0]] = true;
    int l, r;
    l = 0;
    r = 1;
    while (r < len) {
	if (!used[ps[r]]) {
	    s++;
	    used[ps[r]] = true;
	    if (s >= maxi) {
		maxi = s;
		res = ori[l];		
	    }
	} else {
	    while (ps[l] != ps[r]) {
		s--;
		used[ps[l]] = false;
		l++;
	    }	    
	    l++;
	    if (s == maxi) {
		res = ori[l];
	    }
	}
	r++;
    }
    return res;
}

int main() {
    int k, n;
    scanf("%d%d", &k, &n);
    printf("%d\n", solve(k, n));
}