#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
const ll MOD = 1000000007;
const ll INF = 1e18;
#define REP(i, n) for(int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()

int main() {
	int t; scanf("%d",&t);
	vector<bool> pr(5000001,1);
	pr[1]=0;
	for(int i=2;i<=5000000;i++){
		if(pr[i]){
			for(int j=i*2;j<=5000000;j+=i)
				pr[j]=0;
		}
	}
	while(t--){
		ll a, p; scanf("%ld %ld",&a,&p);
		if(pr[p])
			printf("1\n");
		else
			printf("-1\n");
	}
	return 0;
}