#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i, s, n) for (int i = (s); i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
using namespace std;
typedef long long ll;

ll N, K, W, H, M, C, V;

const int MAX = 510000;
const int MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

vector<double> cx, cy, c;
 ll MM = 1e12;

void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

bool prime(int n){
    for(int i = 2; i*i <= n; ++i){
        if(n%i == 0) return false;
    }
    return true;
}

int fhash(int n){
    string str = to_string(n);
    int f = 0;
    REP(i, str.size()){
        f += str[i]- '0';
    }
    if(f < 10) return f;
    else return fhash(f);
}

int main(){
    int n,k;
    cin >> k >> n;
    vector<int> p, v;
    for(int i = k; i <= n; ++i){
        if(prime(i)){p.push_back(i); v.push_back(fhash(i));}
    }
    int len = 1;
    int res = 0;
    for(int i = 0; i < p.size(); ++i){
        int l = 0;
        set<int> digit = {1,2,3,4,5,6,7,8,9};
        int count = 9;
        for(int j = 0; j < 10; ++j){
            count--;
            digit.erase(v[i + j]);
            if(digit.size() != count or digit.size() == 0) break;
            ++l;
        }
        if(l >= len){
            res = p[i];
            len = l;
        }
    }
    cout << res;
    return 0;
}