#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;

vector<int> prime_list(int l,int r){//[l,r]に含まれる素数表
    vector<int> li(r+1,1);
    for(int i=2;i<=r;i++){
        if (!li[i]) continue;
        for(int j=2*i;j<=r;j+=i){
            li[j]=0;
        }
    }
    vector<int> res={};
    for(int i=max(2,l);i<=r;i++){
        if (li[i]) res.push_back(i);
    }
    return res;
}

int has(int s){
    int res=0;
    while(s>0){
        res+=s%10;
        s/=10;
    }
    if (res>=10) return has(res);
    return res;
}

int k,n;
int hashmap[10];

void solve(){
    cin >> k >> n;
    vector<int> pri=prime_list(k,n);
    //for(auto p:pri) cout << p << endl;
    int m=pri.size();
    int ans=0,l=0,r=0,w=0;
    while(true){
        r++;
        int ha=has(pri[r-1]);
        while(hashmap[ha]){
            hashmap[has(pri[l])]--;
            l++;
        }
        hashmap[ha]+=1;
        //cout << l << " " << r << endl; 
        rep(i,10){
            //if (hashmap[i]) cout << i << " "; 
        }
        //cout << "" << endl;
        if (w<=r-l){
            w=r-l;
            ans=l;
        } 
        if(r==m) break;
    }
    cout << pri[ans] << endl;
}


int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}