#include using namespace std; using ll = long long; using ld = long double; using ull = unsigned long long; using uint = unsigned int; using vi = vector; using vb = vector; using vd = vector; using vl = vector; using vvi = vector; using vvb = vector; using vvd = vector; using vvl = vector; #define REP(i,n) for(ll i=0; i<(n); ++i) #define FOR(i,b,n) for(ll i=(b); i<(n); ++i) #define ALL(v) (v).begin(), (v).end() #define TEN(x) ((ll)1e##x) template inline string join(const vector& vec, string sep = " ") { stringstream ss; REP(i, vec.size()) ss << vec[i] << ( i+1 == vec.size() ? "" : sep ); return ss.str(); } vb eratosthenes(ll n) { vb t(n+1, true); t[0] = t[1] = false; for(ll i = 2; i <= n; ++i) if (t[i]){ for(ll j = 2*i; j <= n; j += i) t[j] = false; } return t; } vl compress(const vb & t) { vl v; v.reserve((ll)(1.2 * t.size() / log(t.size()))); REP(i, t.size()) if (t[i]) v.push_back(i); return v; } ll min_prime(ll n) { FOR(i, 2, sqrt(n)+1) if (n%i == 0) return i; return 1; } int main() { #ifdef INPUT_FROM_FILE ifstream cin("sample.in"); ofstream cout("sample.out"); #endif cin.tie(0); ios_base::sync_with_stdio(false); cout << fixed << setprecision(30); ll n, m; cin >> n >> m; auto e = eratosthenes(sqrt(m)*50); auto er = compress(e); ll index = er.size() - 1; while (index >= 0 && er[index] * er[index] > m) index--; if (er[index] * er[index] >= n) { ll ma = 0; for (ll i = index; i < er.size() && er[i] * er[index] <= m; ++i) ma = er[i] * er[index]; cout << ma << endl; return 0; } ll ma = 1; ll mai = 1; for (ll i = m; i >= n; --i) { ll x = min_prime(i); if (ma < x) { ma = x; mai = i; } } cout << mai << endl; return 0; }