/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.07.31 23:07:32
**/

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



struct Eratosthenes {
private:
    int N;
public:
    std::vector< bool > isprime;
    std::vector< int > prime;
    Eratosthenes(int n) : N(n) {
        isprime.resize(N + 1, true);
        isprime[0] = isprime[1] = false;
        for (int i = 2; i * i <= N; i++) {
            if (isprime[i]) {
                for (int j = i + i; j <= N; j += i) {
                    isprime[j] = false;
                }
            }
        }
        for (int i = 2; i <= N; i++) {
            if (isprime[i]) {
                prime.push_back(i);
            }
        }
    }
};
int main() {
    int t;cin >> t;
    Eratosthenes era(5 * 1000000);
    while(t--) {
        ll a, p;
        cin >> a >> p;
        if (era.isprime[p]) {
            cout << 1 << endl;
        }
        else {
            cout << -1 << endl;
        }
    }
    return 0;
}