#include <bits/stdc++.h>
#define FOR(i, a, n) for(ll i = (ll)a; i < (ll)n; i++)
#define FORR(i, n) for(ll i = (ll)n - 1LL; i >= 0LL; i--)
#define rep(i, n) FOR(i, 0, n)
#define ALL(x) begin(x), end(x)
using namespace std;
using ll = long long;
constexpr ll Mod = 998244353;
constexpr ll mod = 1e9 + 7;
constexpr ll inf = 1LL << 60;
const double PI = acos(-1);
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
    return a < b && (a = b, true);
}
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
    return a > b && (a = b, true);
}
/*-------------------------------------------*/

bool isPrime(ll p) {
    if(p == 2) return true;
    if(p < 2 || p % 2 == 0) return false;
    for(ll i = 3; i * i < p; i += 2)
        if(p % i == 0) return false;
    return true;
}

ll solve(ll a, ll p) {
    if(!isPrime(p)) return -1;
    return 1;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int t;
    cin >> t;
    while(t--) {
        ll a, p;
        cin >> a >> p;
        cout << solve(a, p) << "\n";
    }

    return 0;
}