# include <iostream>
# include <algorithm>
#include <array>
# include <cassert>
#include <cctype>
#include <climits>
#include <numeric>
# include <vector>
# include <string>
# include <set>
# include <map>
# include <cmath>
# include <iomanip>
# include <functional>
# include <tuple>
# include <utility>
# include <stack>
# include <queue>
# include <list>
# include <bitset>
# include <complex>
# include <chrono>
# include <random>
# include <limits.h>
# include <unordered_map>
# include <unordered_set>
# include <deque>
# include <cstdio>
# include <cstring>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
constexpr long long MOD = 1000000000 + 7;
constexpr long long INF = std::numeric_limits<long long>::max();
const double PI = acos(-1);
#define fir first
#define sec second
typedef pair<LL, LL> Pll;
typedef pair<LL, pair<LL, LL>> Ppll;
typedef pair<LL, pair<LL, bitset<100001>>> Pbll;
typedef pair<LL, pair<LL, vector<LL>>> Pvll;
typedef pair<LL, LL> Vec2;
struct Tll { LL first, second, third; };
typedef pair<LL, Tll> Ptll;
#define rep(i,rept) for(LL i=0;i<rept;i++)
#define Mfor(i,mf) for(LL i=mf-1;i>=0;i--)
LL h, w, n, m, k, s, t, q, sum, last[10], ans, cnt, a[200010],b[200010], dp[200010];
struct Edge { LL to, cost,mon; };
string str;
bool f[200010];
void YN(bool f) {
	if (f)
		cout << "YES" << endl;
	else
		cout << "NO" << endl;
}
void yn(bool f) {
	if (f)
		cout << "Yes" << endl;
	else
		cout << "No" << endl;
}
vector<Edge>vec[100000];
LL ff(LL x) {
	if (dp[x] != 0)return dp[x];
	if (x / 10 > 0) {
		LL ss = 0, num = x;
		while (num > 0) {
			ss += num % 10;
			num /= 10;
		}
		dp[x] = ff(ss);
	}
	else dp[x] = x;
	return dp[x];
}
int main() {
	cin >> n >> m;
	f[1] = 1;
	for (int i = 2; i*i <= m; i++) {
		if (!f[i])
			for (int j = 2; j*i <= m; j++) {
				f[i*j] = 1;
			}
	}
	for(int i=n;i<=m;i++)
		if (!f[i]) {
			a[cnt] = ff(i);
			b[cnt] = i;
			cnt++;	
		}
	rep(i, cnt) {
		bitset<10>bi = {};
		LL j = i;
		while (j<cnt) {
			if (bi[a[j]] == 1)
				break;
			bi[a[j]] = 1;
			j++;
		}
		if (s <= bi.count()) {
			s = bi.count();
			ans = b[i];
		}
	}
	cout << ans << endl;
	return 0;
}