#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,s,n) for (int i = (s); i < (n); ++i)
#define rrep(i,n,g) for (int i = (n)-1; i >= (g); --i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define len(x) (int)(x).size()
#define dup(x,y) (((x)+(y)-1)/(y))
#define pb push_back
#define eb emplace_back
#define Field(T) vector<vector<T>>
using namespace std;
using ll = long long;
using ull = unsigned long long;
template<typename T> using pq = priority_queue<T,vector<T>,greater<T>>;
using P = pair<int,int>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}

void solve() {
  int n, k;
  cin >> n >> k;
  if (n == k) {
    cout << -1 << endl;
    return;
  }
  if (k <= (n-1)/k) {
    cout << n << endl;
    return;
  }
  do {
    int x = n;
    for (int d = 2; d*d <= x && d < k; ++d) {
      if (x%d == 0) {
        while(x%d == 0) x /= d;
      }
    }
    if (x > k) {
      cout << n << endl;
      return;
    }
  } while(n--);
}

int main() {
  int t;
  cin >> t;
  while(t--) solve();
  return 0;
}