#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll L, R;
    cin >> L >> R;
    int m = 100000;
    const int INF = 1 << 30;
    vector<int> tb(m + 1, INF), p;
    p.reserve(10000);
    tb[0] = tb[1] = 0;
    for(int i = 2; i <= m; i++){
        if(tb[i] != INF) continue;
        p.emplace_back(i);
        for(int j = i; j <= m; j += i) tb[j] = min(tb[j], i);
    }
    auto f = [&](ll v){
        if(v <= m) return tb[v];
        for(int i = 0; i < p.size() && p[i] * p[i] <= v; i++){
            if(v % p[i] == 0){
                do{
                    v /= p[i];
                }while(v % p[i] == 0);
            }
        }
        return INF;
    };
    ll ans = 0, mn_prime = -1;
    for(int i = p.size() - 1; i >= 0 && p[i] >= mn_prime; i--){
        ll bl = max((L + p[i] - 1) / p[i], 2ll);
        bl = max(bl, mn_prime);
        for(ll j = R / p[i]; j >= bl; j--){
            ll v = f(j);
            if(p[i] < v) v = p[i];
            if(v > mn_prime || (v == mn_prime && p[i] * j > ans)){
                mn_prime = v;
                ans = p[i] * j;
            }
        }
    }
    cout << ans << '\n';
}