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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    
    int t;
    cin >> t;
    while (t--) {
        int n, k;
        cin >> n >> k;

        redo:
        if (n == k) {
            cout << "-1\n";
            continue;
        }

        // This is the CORRECT lower bound: (n-1)/k + 1
        // Any number with all factors <= k must have a divisor in this range
        for (int i = (n - 1) / k + 1; i * i <= n; i++) {
            if (n % i == 0) {
                n--;
                goto redo;
            }
        }
        cout << n << "\n";
    }
    return 0;
}