#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

vector<bool> sieve(int n){
    vector<bool> ret(n+1,true);
    ret[0]=false;
    if(n>0) ret[1]=false;
    for(int i=2;i*i<=n;i++){
        if(!ret[i]) continue;
        for(int j=i*2;j<=n;j+=i) ret[j]=false;
    }
    return ret;
}

signed main(){
    auto tmp=sieve(100010);
    vector<ll> P;
    rep(i,100010)if(tmp[i]) P.push_back(i);

    ll L,H;cin>>L>>H;
    
    unordered_set<ll> st;
    st.insert(1);

    reverse(ALL(P));
    
    for(auto &x:P){
        if(L<=x and x<=H) continue;
        if(x>H) continue;
        unordered_set<ll> nx;
        
        ll res=-1;

        for(auto &y:st){
            for(ll w=1;y*w<=H;w*=x){
                if(L<=y*w and y*w<=H) chmax(res,y*w);
                
                if(y*w<=H) nx.insert(y*w);
            }
        }
        if(res!=-1){
            cout<<res<<endl;
            return 0;
        }
        swap(nx,st);
    }
    return 0;
}