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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t; cin >> t;
    while(t--) {
        ll n, k;
        cin >> n >> k;
        
        if(n == k) {
            cout << "-1\n";
            continue;
        }
        
        ll cur = n;
        while(true) {
            if(cur <= k) {
                cout << "-1\n";
                break;
            }
            bool bad = false;
            for(ll i = 2; i * i <= cur; i++) {
                if(cur % i == 0) {
                    bad = true;
                    break;
                }
            }
            if(!bad || (cur > 1 && cur > k)) {
                cout << cur << "\n";
                break;
            }
            cur--;
        }
    }
}