#include <iostream>
#include <algorithm>
#include <cstring>
#include <climits>
#include <vector>
#define getBit(x,b) (x)&(1<<(b))
#define setBit(x,b) (x)|(1<<(b))
#define delBit(x,b) (x)&~(1<<(b))
#define N_MAX 200000
using namespace std;

int calcHash(int n)
{
	int ans = 0;

	while (n > 0)
	{
		ans += n % 10;
		n /= 10;
	}

	if (ans >= 10)
		ans = calcHash(ans);

	return ans;
}

vector<int>* calcPrime(int K, int N)
{
	auto list = new bool[N + 1];
	auto prime = new vector<int>();
	int sn = (int)sqrt(N);

	list[0] = list[1] = false;
	for (int i = 2; i <= N; ++i)
		list[i] = true;

	for (int i = 2; i <= sn; ++i)
	{
		if (list[i])
		{
			int jmax = N / i;
			for (int j = i; j <= jmax; ++j)
				list[i*j] = false;
		}
	}

	for (int i = K; i <= N; ++i)
	{
		if (list[i])
			prime->push_back(i);
	}

	delete[] list;

	return prime;
}

int main()
{
	int K, N, NumPrime, BitChain = 0, max = 0, ans;
	cin >> K >> N;

	int pos[10], index = 0;
	auto prime = calcPrime(K, N);
	NumPrime = prime->size();
	ans = (*prime)[0];
	for (int i = 0; i < 10; ++i)
	{
		pos[i] = -1;
	}

	for (auto it = prime->rbegin(); it != prime->rend(); ++it)
	{
		int h = calcHash(*it);

		if (pos[h] != -1)
		{
			int count = 0;

			for (int i = 0; i < 10; ++i)
			{
				if (pos[i] != -1)
					++count;

				if (pos[i] < pos[h])
				{
					pos[i] = -1;
				}
			}

			if (count > max)
			{
				max = count;
				ans = *(it - 1);
			}

			if (count == 10)
				break;
		}

		pos[h] = index;

		++index;
	}

	cout << ans << endl;

	delete prime;

	return 0;
}