#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>

#define INF 1000000000

using namespace std;
typedef long long ll;

const int MAXN = 400200;
bool isPrime[MAXN];
vector<int> prime;
bool flag[10];

int getHash(int n) {
    if (n < 10) return n;
    string s = to_string(n);
    int ret = 0;
    for (int i = 0; i < s.size(); i++) {
        ret += s[i] - '0';
    }
    return getHash(ret);
}

void createPrime() {
    for (int i = 2; i < MAXN; i++) isPrime[i] = true;
    for (int i = 2; i * i < MAXN; i++) {
        if (isPrime[i]) {
            for (int j = 2; i * j < MAXN; j++) {
                isPrime[i*j] = false;
            }
        }
    }
    for (int i = 2; i < MAXN; i++) {
        if (isPrime[i]) prime.push_back(i);
    }
}

int main(void) {
    createPrime();
    int K, N;
    cin >> K;
    cin >> N;
    int startIndex = 0;
    int endIndex = 0;
    for (int i = 0; ; i++) {
        if (prime[i] >= K) {
            startIndex = i;
            break;
        }
    }
    for (int i = startIndex; ; i++) {
        if (prime[i] > N) {
            endIndex = i;
            break;
        }
    }
//    cout << startIndex << "  " << endIndex << endl;
    // しゃくとり法
    int ansIndex = -1;
    int maxLength = 0;
    int s = startIndex, t = startIndex;
    while (1) {
        // collisionするまで長さを増やす
//        cout << "start " << s << endl;
        while (t < endIndex) {
            int tmp = getHash(prime[t]);
            if (flag[tmp]) break;
            else {
                flag[tmp] = true;
                t++;
            }
        }
//        cout << "end " << t << endl;
        if (maxLength <= t - s) {
            ansIndex = s;
            maxLength = t-s;
        }
        flag[getHash(prime[s])] = false;
        s++;
        if (t >= endIndex) break;
    }
    cout << prime[ansIndex] << endl;
    return 0;
}