#include <bits/stdc++.h>
#define MOD 1000000007LL
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

int t;
bool prime[5000005];
ll fact[500005];

void solve(){
	ll a,p;
	scanf("%lld%lld",&a,&p);
	if(!prime[p]){
		printf("-1\n");
	}else{
		printf("1\n");
	}
}

int main(void){
	memset(prime,true,sizeof(prime));
	prime[0]=prime[1]=false;
	for(ll i=2;i<=5000000;i++){
		if(prime[i]){
			for(int j=i*2;j<=5000000;j+=i){
				prime[j]=false;
			}
		}
	}
	scanf("%d",&t);
	for(int i=0;i<t;i++){
		solve();
	}
	return 0;
}