#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define REP(i,m,n) for(int i=(int)(m); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define RREP(i,m,n) for(int i=(int)(m); i>=(int)(n); i--)
#define rrep(i,n) RREP(i,n-1,0)
#define all(v) v.begin(), v.end()
const int inf = 1e9+7;
const ll longinf = 1LL<<60;
const ll mod = 1e9+7;
const ld eps = 1e-10;

bool arr[1000000000];
set<ll> primes;
void Eratosthenes(int N) {
  for(int i=0; i<N; i++) {
    arr[i] = true;
  }
  for(int i=2; i<sqrt(N); i++) {
    if(arr[i]) {
      for(int j=0; i*(j+2)<N; j++) {
        arr[i*(j+2)] = false;
      }
    }
  }

  for(int i=2; i<N; i++) {
    if(arr[i]) {
      primes.insert(i);
    }
  }
}
ll modpow(ll a, ll N, ll mod=mod) {
  ll ans = 1;
  ll tmp = a;
  while(N > 0) {
    if(N % 2 == 1) (ans *= tmp) %= mod;
    (tmp *= tmp) %= mod;
    N /= 2;
  }
  return ans;
}
void solve() {
  ll a, p; cin >> a >> p;
  if(!primes.count(p)) cout << -1 << "\n";
  else cout << 1 << "\n";
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  Eratosthenes(5000005);
  int t; cin >> t;
  while(t--) {
    solve();
  }
  return 0;
}