Codeforces Round #412 (rated, Div. 2, base on VK Cup 2017 Round 3) A Is it rated?

地址：http://codeforces.com/contest/807/problem/C

题目：

C. Success Rate time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output

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?

Input

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.

Output

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.

Example input

4
3 10 1 2
7 14 3 8
20 70 2 7
5 6 1 1

output

4
10
0
-1

Note

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.

 思路：略

#include <bits/stdc++.h>

using namespace std;

#define MP make_pair
#define PB push_back
typedef long long LL;
typedef pair<int,int> PII;
const double eps=1e-8;
const double pi=acos(-1.0);
const int K=1e6+7;
const int mod=1e9+7;

int p,x,y;

int main(void)
{
//std::ios::sync_with_stdio(false);
//std::cin.tie(0);
int n;
LL x,y,p,q,x1,x2,ans;
scanf("%d",&n);
for(int i=1;i<=n;i++)
{
scanf("%I64d%I64d%I64d%I64d",&x,&y,&p,&q);
if(p==0)
{
if(x!=0)
printf("-1\n");
else
printf("0\n");
}
else if(p==q)
{
if(x!=y)
printf("-1\n");
else
printf("0\n");
}
else
{
x1=(q*x-y*p)/p;
if(x1*p<(q*x-y*p))
x1++;
x2=(y*p-x*q)/(q-p);
if(x2*(q-p)<(y*p-x*q))
x2++;
ans=max(x1,x2)+y;
if(ans%q)
ans=((ans/q)+1)*q-y;
else
ans=ans-y;
printf("%I64d\n",ans);
}

}
return 0;
}