#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i)) #define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i)) #define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i)) #if defined(_MSC_VER) || __cplusplus > 199711L #define aut(r,v) auto r = (v) #else #define aut(r,v) __typeof(v) r = (v) #endif #define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it) #define all(o) (o).begin(), (o).end() #define pb(x) push_back(x) #define mp(x,y) make_pair((x),(y)) #define mset(m,v) memset(m,v,sizeof(m)) #define INF 0x3f3f3f3f #define INFL 0x3f3f3f3f3f3f3f3fLL using namespace std; typedef vector vi; typedef pair pii; typedef vector > vpii; typedef long long ll; template inline void amin(T &x, U y) { if(y < x) x = y; } template inline void amax(T &x, U y) { if(x < y) x = y; } vector isprime; vector primes; void sieve(int n){ if((int)isprime.size() >= n+1) return; isprime.assign(n+1, true); isprime[0] = isprime[1] = false; int sqrtn = (int)(sqrt(n * 1.) + .5); for(int i = 2; i <= sqrtn; i ++) if(isprime[i]) { for(int j = i * i; j <= n; j += i) isprime[j] = false; } primes.clear(); for(int i = 2; i <= n; i ++) if(isprime[i]) primes.push_back(i); } int f(int n) { return (n - 1) % 9 + 1; } int main() { int L, R; while(cin >> L >> R) { sieve(R + 100); int i = lower_bound(all(primes), L) - primes.begin(), j = i; pii ans(0, 0); vector v(10, false); for(; primes[i] <= R; ++ i) { for(; primes[j] <= R && !v[f(primes[j])]; ++ j) v[f(primes[j])] = true; amax(ans, mp(j - i, primes[i])); v[f(primes[i])] = false; } printf("%d\n", ans.second); } return 0; }