#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
bool b[200020] = { false };
vector<int> vec;
int main() {
    int l, r;
    cin >> l >> r;
    b[1] = true;
    for (int i = 2; i <= 200000; i++) {
        if (!b[i]) {
            for (int j = i + i; j <= 200000; j += i) {
                b[j] = true;
            }
        }
    }
    for (int i = l; i <= r; i++) {
        if (!b[i]) {
            vec.emplace_back(i);
        }
    }
    int n = vec.size();
    int ans = 0, ans1;
    set<int> st;
    int right = 0;
    for (int left = 0; left < n; left++) {
        while (right < n) {
            auto itr = st.find(vec[right] % 9);
            if (itr != st.end() && st.size() != 0) {
                break;
            }
            st.insert(vec[right] % 9);
            right++;
        }
        if (ans <= right - left - 1) {
            ans = right - left - 1;
            ans1 = left;
        }
        if (right == left) {
            right++;
        }
        else {
            st.erase(vec[left] % 9);
        }
    }
    cout << vec[ans1] << endl;
}