#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repp(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define int long long
using namespace std;

vector<int> prime;
bool isprime[100010];

void sieve(int n){
    rep(i, 0, n + 1) isprime[i] = true;
    isprime[0] = isprime[1] = false;
    rep(i, 2, n + 1){
        if(isprime[i]) prime. push_back(i);
        for(int j = 2*i; j <= n; j += i) isprime[j] = false;
    }
    return;
}

signed main(){
    int l, h, a, ans = -1;
    cin >> l >> h;
    sieve(100000);
    a = prime.back();
    if(h - l >= a){
        rep(i, 0, 200000){
            if(i*a > h){
                ans = a*(i - 1);
                break;
            }
        }
    }else{
        vector<int> cand;
        bool f[100010];
        memset(f, true, sizeof(f));
        rep(i, 0, prime.size()){
            int st = (l - 1) / prime[i] + 1;
            for(int j = st*prime[i]; j <= h; j += prime[i]){
                if(j != prime[i] && f[j - l] == true) cand. push_back(j);
                f[j - l] = false;                
            }
        }
        ans = cand.back();
    }
    cout << ans << endl;
}