func_code_string: #include <bits/stdc++.h>   #pragma GCC optimize( O3 )   using namespace std;   const int mod = (int)1e9 + 7;   const long long INF = 1000000000000000000LL;   const int WASTE = (int)2e5;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(NULL);     cout.tie(NULL);     int t;     cin >> t;     while (t--) {       int x, y, p, q;       cin >> x >> y >> p >> q;       if (!p) {         cout << (x == 0 ? 0 : -1) <<   n ;         continue;       }       if (p == q) {         if (x == y)           cout << 0 <<   n ;         else           cout << -1 <<   n ;         continue;       }       int i = (x + p - 1) / p;       int i1 = (y - x - p + q - 1) / (q - p);       cout << (q * 1LL * max(i, i1) - y) <<   n ;     }     return 0;   }   