#include "bits/stdc++.h"
using namespace std;

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

const int MAX_N = 200000 + 10;
bool is_prime[MAX_N];


int main() {

	for (int i = 0; i < MAX_N; i++) is_prime[i] = true;
	is_prime[0] = is_prime[1] = false;
	for (int i = 2; i * i <= MAX_N; i++) {
		if (is_prime[i]) {
			for (int j = i * i; j < MAX_N; j += i) {
				is_prime[j] = false;
			}
		}
	}

	int A, B;
	cin >> A >> B;
	vector<int> primes;
	for (int i = A; i <= B; i++) if (is_prime[i]) primes.push_back(i);

	int bestLen = 0;
	int start = 0;
	for (int len = 1; len <= 9; len++) {
		for (int s = 0; s + len <= primes.size(); s++) {
			int mask = 0;
			bool ok = true;
			for (int i = s; i < s + len; i++) {
				int v = primes[i] % 9;
				if (mask & (1 << v)) {
					ok = false;
					break;
				}
				mask |= (1 << v);
			}
			if (ok) {
				if (bestLen <= len) {
					bestLen = len;
					start = primes[s];
				}
			}
		}
	}
	cout << start << endl;


}