#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef complex<double> P;
typedef pair<int,int> pii;
#define REP(i,n) for(ll i=0;i<n;++i)
#define REPR(i,n) for(ll i=1;i<n;++i)
#define FOR(i,a,b) for(ll i=a;i<b;++i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define MOD (ll)(1e9+7)
#define ADD(a,b) a=((a)+(b))%MOD
#define FIX(a) ((a)%MOD+MOD)%MOD

ll L,H;
bool isp[100000];
vl ps;

ll pow(ll a,ll b){
  ll r = 1;
  while(b){
    if(b&1)r=r*a;
    a=a*a;
    b>>=1;
  }
  return r;
}

int main(){
  scanf("%lld%lld",&L,&H);
  REP(i,100000)isp[i]=true;
  isp[0]=isp[1]=false;
  FOR(x,2,100000){
    if(!isp[x])continue;
    ps.push_back(x);
    {
      int it = x+x;
      while(it<100000){
        isp[it]=false;
        it+=x;
      }
    }
  }
  if(H-L<50000){
    // brute-force
    ll mx = L-1;
    ll mfct = 0;
    FOR(x,L,H+1){
      REP(i,ps.size()){
        ll p = ps[i];
        if(x<=p)break;
        if(x%p==0){
          if(p>=mfct){
            mfct = p;
            mx = x;
          }
          break;
        }
      }
    }
    printf("%lld\n",mx);
  }else{
    set<ll> dp;
    dp.insert(1);
    FOR(i,0,ps.size()){
      ll x = ps[ps.size()-1-i];
      ll ans = -1;
      for(ll p : dp){
        if(p*x>H)break;
        dp.insert(p*x);
        if(p!=1 && L<=p*x){
          ans = max(ans,p*x);
        }
      }
      if(ans!=-1){
        printf("%lld\n",ans);
        return 0;
      }
    }
  }
  return 0;
}