#include "bits/stdc++.h"

#define REP(i,num) for(ll i=0;i<(num);++i)
#define FOR(i,c,num) for(ll (i)=(c);(i)<(num);++(i))
#define LOOP(i) while(i--)
#define ALL(c) c.begin(),c.end()
#define PRINTALL(c) for(auto pitr=c.begin();pitr!=c.end();++pitr){cout<<*pitr;if(next(pitr,1)!=c.end())cout<<' ';}cout<<endl;
#define PAIRCOMP(c,comp) [](const pair<ll,ll>& lhs,const pair<ll,ll>& rhs){return lhs.c comp rhs.c;}

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;

constexpr ll atcoder_mod = 1e9+7;

template<typename T=ll>
T in(){ T x; cin >> x; return (x); }
template<typename T=ll,typename C=vector<T>>
C vecin(int N){ C x(N);REP(i,N){ x[i]=in<T>(); }return x; }

void vout(){ cout << endl; }
template<typename Head,typename... Tail>
void vout(Head&& h,Tail&&... t){ cout << ' ' << h;vout(forward<Tail>(t)...); }
void out(){ cout << endl; }
template<typename Head,typename... Tail>
void out(Head&& h,Tail&&... t){ cout << h;vout(forward<Tail>(t)...); }

template<typename T>
bool chmax(T& a,T b){ if(a<b){ a=b;return true; }return false; }
template<typename T>
bool chmin(T& a,T b){ if(a>b){ a=b;return true; }return false; }

vector<ll> enum_prime(ll N){
	deque<bool> is_prime(N+1,true);
	vector<ll> P;
	for(ll i=2;i<=N;i++){
		if(is_prime[i]){
			for(ll j=i*i;j<=N;j+=i){
				is_prime[j] = false;
			}
			P.emplace_back(i);
		}
	}
	return P;
}

ll Hash(ll V){
	ll X=V;
	while(X/10){
		ll C=0;
		while(X){
			C += X%10;
			X /= 10;
		}
		X = C;
	}
	return X;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);

	auto K=in(),N=in();
	auto KP = enum_prime(K-1);
	auto NP = enum_prime(N);
	vll P,H;
	set_difference(ALL(NP),ALL(KP),back_inserter(P));

	for(auto& x:P){
		H.push_back(Hash(x));
	}
	vll C(10,0);
	ll L=0,R=1,S=H.size(),M=1,A=0;
	C[H[0]]=1;
	while(L<S && R<S){
		while(R<S){
			R++;
			C[H[R-1]]++;
			if(C[H[R-1]]>1) break;
			if(M<=R-L){
				A=L;
				M = max(M,R-L);
			}
		}
		while(C[H[R-1]]>1){
			C[H[L]]--;
			L++;
		}
		if(R==S){
			if(M<=R-L){
				A=L;
				M = max(M,R-L);
			}
		}
	}
	out(P[A]);
	return 0;
}