#include <bits/stdc++.h>
using namespace std;
template <typename T> using min_priority_queue = priority_queue<T,vector<T>,greater<T>>;

template<typename T>
void outvec(vector<T> &v){
    bool b = false;
    for(auto i : v){
        if(b) cout << " ";
        else b = true;
        cout << i;
    }
    cout << endl;
}

template<typename T>
void invec(vector<T> &v){
    for(auto &i : v){
        cin >> i;
    }
}

template <typename T>
bool chmin(T &a, const T& b) {
    if (a > b) {
        a = b;  // aをbで更新
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T &a, const T& b) {
    if (a < b) {
        a = b;  // aをbで更新
        return true;
    }
    return false;
}

void yn(bool b){
    if(b) cout << "Yes" << endl;
    else cout << "No" << endl;
}

bool debug;
bool randomInput;
bool debugOutput;
int numOfTestCase;

using ans_type = int;

void input(){
    if(numOfTestCase > 1){
        ;
    }

    if(randomInput){
        
    }
    else{
        
    }
    return;
}

void output_input(){
    ;
}

int hsh(int x){
    int rtn = 0;
    while(x){
        rtn += x%10;
        x /= 10;
    }
    if(rtn < 10) return rtn;
    else return hsh(rtn);
}

ans_type calc(){
    int K, N; cin >> K >> N;
    vector<bool> V(N+1, true);
    vector<int> P;
    for(int i = 2; i <= N; i++){
        if(V[i]){
            P.push_back(i);
            for(int j = 2 * i; j <= N; j += i){
                V[j] = false;
            }
        }
    }

    vector<int> Q;
    for(int p : P){
        if(K <= p && p <= N) Q.push_back(p);
    }
    int M = Q.size();

    vector<int> H(M);
    for(int i = 0; i < M; i++){
        H[i] = hsh(Q[i]);
    }

    int l = 0;
    int r = 0;
    int s = 0;

    int best_l = 0;
    int best_r = 0;

    while(r < M){
        if(s>>H[r]&1){
            s -= 1<<H[l];
            l++;
        }
        else{
            s += 1<<H[r];
            r++;
        }

        if(r - l >= best_r - best_l){
            best_l = l;
            best_r = r;
        }
    }

    cout << Q[best_l] << endl;

    //outvec(Q);
    return ans_type();
}

ans_type calc_simple(){
    return ans_type();
}

void output(ans_type ans){
    return;
}

int main(){
    debug = 0;
    randomInput = 0;
    debugOutput = 0;
    numOfTestCase = 1;
    srand(time(NULL));
    cout << fixed << setprecision(12);
    
    if(numOfTestCase == 0) cin >> numOfTestCase;

    if(debug){
        for(int i = 0; i < numOfTestCase; i++){
            input();
            ans_type ans = calc();
            ans_type ansSimple = calc_simple();
            if(ans != ansSimple){
                output_input();
                output(ans);
                output(ansSimple);
            }
        }
    }
    else{
        for(int i = 0; i < numOfTestCase; i++){
            input();
            output(calc());
        }
    }

    return 0;
}