// https://kanpurin.hatenablog.com/entry/2022/10/05/012134

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i,l,r) for (int i = l;i < (int)(r); i++)
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

// f_t(s) = gとなる最小のtを求める
// f_i(x) = x + i * K (mod N)
// x = S, g = 0

const ll MOD = 1e9;
const ll M = 33333;

void solve(){
    ll S, K; cin >> K >> S;
    K %= MOD;
    S %= MOD;

    auto f = [&](ll i, ll x0){
        x0 %= MOD;
        i %= MOD;
        return (x0 + (i * K) % MOD) % MOD;
    };

    map<ll,ll> mp;
    for(ll j = 1; j <= M; j++){
        mp[f(j, 0)] = j;
    }

    ll ans = -1;
    for(ll i = 1; i <= (MOD + M - 1) / M; i++){
        if(ans == -1 && mp.find(f(i * M, S)) != mp.end()){
            ans = i * M - mp[f(i * M, S)];
        }
    }
    cout << ans << endl;
}

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int T; cin >> T;
    while(T--) solve();
}