#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll,ll> P;
#define REP(i,n) for(ll i=0;i<ll(n);i++)




ll gcd(ll a,ll b){
	if(b==0) return a;
	else return gcd(b,a%b);
}



ll extgcd(ll a,ll b,ll & x,ll & y){
	ll g;
	if(b!=0){
		g=extgcd(b,a%b,y,x);
		y-=(a/b)*x;
	}else{
                g=a;
		x=1; y=0;
	}
	  return g;
}





int main(void){
	cin.tie(nullptr);  ios_base::sync_with_stdio(false);
	ll i,j;



	int T;
	cin >> T;
	while(T--){

		ll N,M;
		cin >> N >> M;

		ll g=gcd(1000000000,N);
		if(M%g!=0){
			cout << -1 << endl;
			continue;
		}

		ll x,y;
		N*=-1;
		g=extgcd(1000000000,N,x,y);


		ll t=y*M/1000000000;
		vector<ll> v;
		for(i=t-2;i<=t+2;i++){
			v.push_back(M/g*y-1000000000/g*i);
		}

		sort(v.begin(),v.end());


		REP(i,5){
			if(v[i]>0){
				cout << v[i] << endl;
				break;
			}
		}







	}






	return 0;
}