#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <array>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////
const int NumMax = 200000;
//int prime[NumMax];
//int primeMax=0;
//int primeSize=0;
int hashSize = 0;

bool pdp[NumMax+1];
vector<int> prime;
array<int,NumMax> hashList;

void makePrime(int N){
	for(int i=2; i<= N; ++i){
		if(pdp[i] == false){
			prime.push_back(i);
			for(int j = i+i; j<= N; j += i){
				pdp[j] = true;
			}
		}
	}
	return ;
}
int makehash(int num){
	int temp = num;
	int value = 0;
	do{
		while(temp != 0){
			value += temp%10;
			temp /= 10;
		}
		temp  = value;
		value = 0;
	}while(temp >= 10);
	return temp;
}
void makeHashList(int K,int N){
	for(int i=0;i<prime.size();++i){
		{
			//hashList.push_back( makehash( prime[i] ) );
			hashList[hashSize] = makehash( prime[i] );
			++hashSize;
		}
	}
}
int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    cout << setprecision(10);//

	int K,N;
	cin>>K>>N;
	makePrime(N);
	makeHashList(K,N);
	//hashList
	unsigned int maxLen=0;
	int ans = 0;
	unsigned int i=0;

	for(int No = 0; No < prime.size() ; ++No){
		if(prime[No] < K){
			++i;
		}else{
			break;
		}
	}

	for(i; i < hashSize ; ++i){
		set<int> data;
		for(unsigned int j = i;j < hashSize ; ++j){
			if( data.insert(hashList[j]).second != true){
				break;
			}
		}
		if( maxLen <= data.size() ){
			maxLen = data.size();
			ans = prime[i];
		}
	}
	P(ans);
    return 0;
}