Success Rate
题目描述
You are an experienced Codeforces user. Today you found out that during your activity on Codeforces you have made y submissions, out of which x have been successful. Thus, your current success rate on Codeforces is equal to x/y.
Your favorite rational number in the [0;1] range is p/q. Now you wonder: what is the smallest number of submissions you have to make if you want your success rate to be p/q?
The first line contains a single integer t (1≤t≤1000)− the number of test cases.
Each of the next t lines contains four integers x, y, p and q (0≤x≤y≤109; 0≤p≤q≤109; y>0; q>0).
It is guaranteed that p/q is an irreducible fraction.
Hacks. For hacks, an additional constraint of t≤5 must be met.
For each test case, output a single integer equal to the smallest number of submissions you have to make if you want your success rate to be equal to your favorite rational number, or -1 if this is impossible to achieve.
4
3 10 1 2
7 14 3 8
20 70 2 7
5 6 1 1
4
10
0
-1
In the first example, you have to make 4 successful submissions. Your success rate will be equal to 7/14, or 1/2.
In the second example, you have to make 2 successful and 8 unsuccessful submissions. Your success rate will be equal to 9/24, or 3/8.
In the third example, there is no need to make any new submissions. Your success rate is already equal to 20/70, or 2/7.
In the fourth example, the only unsuccessful submission breaks your hopes of having the success rate equal to 1.
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 326 题。保留原作者与原赛事署名。