#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back
#define pcnt __builtin_popcount
#define show(x) cout<<#x<<" = "<<x<<endl;
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define fi first
#define se second
#define rng(a) a.begin(),a.end()
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define sz(x) (int)(x).size()
#define mp make_pair

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pii> vpii;
typedef set<int> si;
typedef pair<ll,ll> pll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pll> vpll;
typedef set<ll> sl;
template<typename T>string join(vector<T>&v)
{stringstream s;FOR(i,0,sz(v))s<<' '<<v[i];return s.str().substr(1);}
ll gcd(ll a,ll b){if(a>b)swap(a,b);for(;a>0;b%=a,swap(a,b));return b;}
int modpow(ll a,ll n,int m){if(a==0)return a;ll p=1;for(;n>0;n/=2,a=a*a%m)if(n&1)p=p*a%m;return(int)p;}
void dout(double d){printf("%.12f\n",d);}

const int iinf = 1e9;
const ll linf = 1e18;
const int mod = 1e9+7;
const double pi = acos(-1);
const double eps = 1e-10;

set<ll> pl;
bool is_prime(ll a){
  if(a < 2)return false;
  each(itr, pl){
    if(*itr * *itr > a) return true;
    if(a % *itr == 0)return false;
  }
  return true;
}
bool is_prime(ll a, ll lim){
  if(a < lim)return false;
  each(itr, pl){
    if(*itr >= lim)return true;
    if(*itr * *itr > a)return true;
    if(a % *itr == 0) return false;
  }
  return true;
}
void set_pl(int a){
  pl.insert(2);
  pl.insert(3);
  for(int i = 5;i <= a;){
    if(is_prime(i)) pl.insert(i);
    i += 2;
    if(is_prime(i)) pl.insert(i);
    i += 4;
  }
}
ll include(ll l, ll r, ll lim){
  if(l > r)return 0;
  for(ll i = r;i >= l; i--) if(is_prime(i, lim))return i;
  return 0;
}
ll L, H;
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  set_pl(1000000);
  cin >> L >> H;
  ll t;
  for(sl::reverse_iterator itr = pl.rbegin(); itr != pl.rend(); itr++){
    t = include((L-1) / *itr + 1, H/ *itr, *itr);
    if(t > 0){
      cout << *itr * t << endl;
      return 0;
    }
  }
  return 0;
}