#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define rep(a,b,c) for(ll a=b;a<c;a++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

void get(vll &a){re(i,a.size()) scanf("%lld",&a[i]);}
void get(vvl &a){re(i,a.size()) re(j,a[0].size()) scanf("%lld",&a[i][j]);}
void print(vll &a){re(i,a.size()) cout<<a[i]<<(i==a.size()-1?"\n":" ");}
void print(vvl &a){re(i,a.size()) re(j,a[0].size())cout<<a[i][j]<<(j==a[0].size()-1?"\n":" ");}

ll mpow(ll a, ll b, ll p = -1){
  ll ret = 1, num = a;
  if(p==-1){
    while(b>0){
      if(b%2) ret *= num;
      num = num * num;
      b /= 2;
    }
  }else{
    while(b>0){
      if(b%2) ret = (ret*num)%p;
      num = (num*num)%p;
      b /= 2;
    }
  }
  return ret;
}
void solve(){
  ll a, b;std::cin >> a >> b;
  for(ll i=2;i*i<=b;i++){
    if(b%i==0){
      std::cout << -1 << '\n';
      return;
    }
  }
  std::cout << 1 << '\n';
}
int main(int argc, char const *argv[]) {
  ll t;std::cin >> t;
  re(i, t) solve();
  return 0;
}