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

const int MAXP = 1000010;
vector<int> primes;
bitset<MAXP> isp;

void sieve() {
    isp.set(); isp[0]=isp[1]=0;
    for (long long i = 2; i < MAXP; i++) if (isp[i]) {
        primes.push_back(i);
        for (long long j = i*i; j < MAXP; j += i) isp[j]=0;
    }
}

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    sieve();
    int T; cin >> T;
    while (T--) {
        int n, k; cin >> n >> k;
        if (n == k) { cout << "-1\n"; continue; }

        long long ans = -1;

        // Try every prime p > k
        for (int p : primes) {
            if (p > k) {
                if (p > n) break;
                ans = max(ans, (long long)(n / p) * p);
            }
        }

        // If n itself has a prime factor > k ? n is also a candidate
        int x = n;
        for (int p : primes) {
            if ((long long)p * p > x) break;
            while (x % p == 0) x /= p;
        }
        if (x > k) ans = max(ans, (long long)n);

        cout << (ans == -1 ? -1 : ans) << "\n";
    }
}