#include <bits/stdc++.h>
#include <atcoder/all>
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

int main()
{
    int t;
    cin >> t;
    while(t--) {
        ll a, b;
        cin >> a >> b;
        ll ans = 1e18;
        for(ll c=2;c*c<=1e9+5;c++){
            ll val = b - c * a;
            if(val<0) break;
            if(val%(c-1)==0) {
                ans = min(ans, val/(c-1));
            }
        }
        for(ll x=0;x*x<=1e9+5;x++){
            if((b+x)%(a+x)==0) {
                ans = min(ans, x);
            }
        }   
        if(ans==1e18) ans = -1;
        cout << ans << endl;
    }
    return 0;
}