#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 int MOD = 998244353;
const int MOD2 = 1e9+7;
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

vector<ll> make_divisors(ll n){
    vector<ll> divisors;
    ll i = 1;
    while (i * i <= n){
        if (n % i == 0){
            divisors.push_back(i);
            if (i != (n/i)) divisors.push_back(n/i);
        }
        i++;
    }
    sort(all(divisors));
    return divisors;
}

void solve(){
    ll A, B; cin >> A >> B;
    vector<ll> divs = make_divisors(B - A);
    ll ans = LINF;
    for(auto &d : divs){
        ll c = d + 1;
        if(c > (B / A)) continue;
        chmin(ans, (B - c * A) / (c - 1));
    }
    debug(divs);

    cout << (ans < LINF ? ans : -1) << endl;
}

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