func_code_string: #include <bits/stdc++.h>   using namespace std;   long long x, y, p, q;   bool check(long long t) {     return ((p * t >= x) && ((q * t - p * t) >= (y - x)));   }   int main() {     int t;     scanf( %d , &t);     while (t--) {       scanf( %I64d%I64d%I64d%I64d , &x, &y, &p, &q);       long long l = 0, r = 1e9, mid;       long long ans = -1;       while (l <= r) {         mid = (l + r) / 2;         if (check(mid)) {           ans = mid;           r = mid - 1;         } else           l = mid + 1;       }       if (ans == -1)         printf( -1 n );       else         printf( %I64d n , ans * q - y);     }     return 0;   }   