#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={0,1,-1,0,1,1,-1,-1,0};
const ll dx[9]={1,0,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
} 


class osak{
    public:
    vector<long long> res;
    vector<long long> prime;
    osak(long long n){//sieve(n),O(N);
        res=vector<long long>(n);
        iota(res.begin(), res.end(), 0);
        for (int i = 2; i*i < n; ++i) {
            if (res[i] < i) continue;
            for (int j = i*i; j < n; j += i)
            if (res[j] == j) res[j] = i;
        }
        for(int i = 2; i < n; ++i){
            if(res[i]==i)prime.emplace_back(i);
        }
    }

    map<long long,long long> factor(int n) {
        map<long long,long long> factor;
        while (n > 1) {
            factor[res[n]]++;
            n /= res[n];
        }
        return factor;
    }

    vector<long long> divisor(int N){//O(div.size())
        map<long long,long long> facs=factor(N);
        vector<long long> ret={1};
        for(auto p:facs){
            ll range=ret.size();
            ll now=1;
            for(int i=0;i<p.se;i++){
                now*=p.fi;
                for(int j=0;j<range;j++){
                    ret.emplace_back(ret[j]*now);
                }
            }
        }
        sort(ret.begin(),ret.end());
        return ret;
    }
};
ll dp[11500010];
int main(){
    ll l,r;cin >> l >> r;
    osak os(100000);
    auto prime=os.prime;
    if(r-l>11500000){
        ll mp=0;
        for(auto p:prime){
            if(l<=p*p&&p*p<=r)mp=p;
        }
        ll ans=0;
        for(auto p:prime){
            if(l<=p*mp&&p*mp<=r)ans=p*mp;
        }
        cout << ans << endl;
    }
    else{
        rep(i,r-l+1)dp[i]=i+l;
        for(auto p:prime){
            for(ll i=(l+p-1)/p*p;i<=r;i+=p){
                if(dp[i-l]!=i)continue;
                dp[i-l]=p;
            }
        }
        //rep(i,r-l+1)cout << dp[i] <<" ";cout << endl;
        ll idx=0,ans=0;
        per(i,r-l+1){
            if(dp[i]==i+l)continue;
            if(chmax(idx,dp[i]))ans=i+l;
        }
        cout << ans << endl;
    }
}