#include <bits/stdc++.h>
#include <atcoder/all>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

// 返り値: a と b の最大公約数
// ax + by = gcd(a, b) を満たす (x, y) が格納される
long long extGCD(long long a, long long b, long long &x, long long &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    long long d = extGCD(b, a%b, y, x);
    y -= a/b * x;
    return d;
}

//aのmod mでの逆元を求める
long long mod_inverse(long long  a, long long m) {
	long long x, y;
	extGCD(a, m, x, y);
	return (m + x % m) % m;
}

int main()
{
    int t;
    cin >> t;
    while(t--) {
        ll n, m;
        cin >> n >> m;
        ll g = gcd(n,(ll)1e9);
        m = -m+1e9;
        if(m%g) {
            cout << -1 << endl;
            continue;
        }
        ll x, y;
        ll G = extGCD(n,1e9,x,y);
        x *= m/g;
        y *= m/g;
        x = (x%(int)1e9+(int)1e9)%(int)1e9;
        cout << x << endl;
    }
    return 0;
}