#include #define rep(i,n) for(int i = 0; i < (n); ++i) #define srep(i,s,t) for (int i = s; i < t; ++i) #define drep(i,n) for(int i = (n)-1; i >= 0; --i) using namespace std; typedef long long int ll; typedef pair P; #define yn {puts("Yes");}else{puts("No");} #define MAX_N 200005 /* Max_Prime以下の素数をprimes[]に格納 */ const int Max_Prime = 1000000; int tmp_primes[Max_Prime]; vector primes; void PrimeInit() { rep(i,Max_Prime)tmp_primes[i] = 1; tmp_primes[0] = 0; tmp_primes[1] = 0; rep(i,Max_Prime){ if(tmp_primes[i] == 0)continue; int j = 2; while(i * j < Max_Prime){ tmp_primes[i*j] = 0; j++; } } rep(i,Max_Prime){ if(tmp_primes[i])primes.push_back(i); } } int suujikonn(ll x){ if(x < 0) return -1; else if(x == 0) return 0; else if(x % 9 == 0) return 9; else return x % 9; } int main() { int k, n; cin >> k >> n; PrimeInit(); int ma = 0; int ans = 0; int m = primes.size(); int f[m] = {}; int cnt[10] = {}; int l = 0; int now = 0; rep(i,m){ int x = primes[i]; if(x < k){ l = i + 1; continue; } if(x > n) break; f[i] = suujikonn(x); cnt[f[i]]++; while(cnt[f[i]] > 1){ cnt[f[l]]--; l++; } if(i-l+1>=ma){ ma = i-l+1; ans = primes[l]; } } cout << ans << endl; return 0; }