#include <bits/stdc++.h>
using namespace std;
/*/
#include <atcoder/all>
using namespace atcoder;
#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector,fast-math")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#pragma GCC target("avx,avx2,fma")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
//*/
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,a,b) for(int i=a;i<b;i++)
#define ALL(x) (x).begin(),(x).end()
#define dbgv(x); for(auto now : x) cout << now << " "; cout << endl;
//using P = pair<int,int>;
using ll = long long;
using ull = unsigned long long;
//*/
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; }
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<int> vint;
random_device rnd;
mt19937 rng(rnd());


vector<long long> divisor(long long n) {
    vector<long long> ret;
    for (long long i = 1; i*i <= n; i++) {
        if (n % i == 0) {
            ret.push_back(i);
            if(n/i != i) ret.push_back(n/i);
        }
    }
    sort(ret.begin(),ret.end());
    return ret;
}


void solve(){
  ll a,b; cin >> a >> b;
  if(b%a==0){
    cout << 0 << endl;
    return;
  }
  auto v = divisor(b-a);
  const ll INF = 1e18;
  ll ans = INF;
  rep(i,v.size()){
    if(a*(v[i]+1) > b) break;
    else chmin(ans,(b-(v[i]+1)*a)/(v[i]));
  }
  if(ans == INF) cout << -1 << endl;
  else cout << ans << endl;
}


int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int t = 1; cin >> t;
  rep(testcases,t) solve();
}