#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000000
#define Inf64 1000000000000000001LL

int main(){
	
	int _t;
	cin>>_t;
	rep(_,_t){
		long long N,M;
		cin>>N>>M;
		long long mod = 1000000000;
		N %= mod;
		M %= mod;
		M *= -1;
		M %= mod;
		M += mod;
		M += mod;
		M %= mod;
		long long g = gcd(N,M);
		g = gcd(g,mod);
		N /= g;
		M /= g;
		if(gcd(N,mod)!=1)cout<<-1<<endl;
		else{
			M *= inv_mod(N,mod);
			M %= mod;
			if(M==0)M = mod;
			cout<<M<<endl;
		}
		
	}
	return 0;
}