#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define mem(a) memset(a,0,sizeof(a))
#define pd(a) printf("%.10f\n",a)
#define pb(a) push_back(a)
#define in(a) insert(a)
#define pi M_PI
#define R cin>>
#define F first
#define S second
#define C class
#define ll long long
#define ln cout<<'\n'
template<C T>void pr(T a){cout<<a;ln;}
template<C T,C T2>void pr(T a,T2 b){cout<<a<<' '<<b;ln;}
template<C T,C T2,C T3>void pr(T a,T2 b,T3 c){cout<<a<<' '<<b<<' '<<c;ln;}
template<C T>void PR(T a,int n){rep(i,n){if(i)cout<<' ';cout<<a[i];}ln;}
bool check(int n,int m,int x,int y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<int,int> P;
vector<ll> sieve(int n) {
  vector<ll> p(n);
  REP(i,2,n) p[i]=i;
  for(int i=2; i*i<n; i++) {
    if(p[i]) {
      for(int j=i*i; j<n; j+=i) p[j]=0;
    }
  }
  p.erase(remove(all(p),0),p.end());
  return p;
}

void Main() {
  vector<ll> p=sieve(1000000);
  ll a,b;
  cin >> a >> b;
  ll ans=0,M=0;
  rep(i,p.size()) {
    ll x=p[i];
    ll y=b/x;
    if(y<=1) break;
    ll z=y*x;
    ll zz=z;
    for(ll j=0; j<p.size()&&p[j]*p[j]<=z; j++) {
      if(z%p[j]==0) {
        zz=p[j];
        break;
      }
    }
    if(a<=z&&z<=b&&M<min(p[i],zz)) {
      ans=z;
      M=min(p[i],zz);
    } else if(M==min(p[i],zz)) ans=max(ans,z);
  }
  pr(ans);
}

int main() {
  ios::sync_with_stdio(0);cin.tie(0);
  Main();return 0;
}