Given four positive integers p, q, x, and y, you can perform an operation that increases both x and y by 1 simultaneously.

Your task is to determine the number of operations needed to meet the condition where px equals qy.

Input Format

The first Line contains 4 space-separated integers p, q, x and y

Output Format

A single integer represents the total number of operations.

If the answer is not possible by any number of operations then print -1.

| Constraints

1>= p, q, x and y <= 100000.

Sample Testcase 1

Testcase Input

2 4 3 1

Testcase Output

1

Explanation

Value of p,q,x,y is 2,4,3,1 if we add 1 to x and y then x will become 4 and y will become 2 so the answer will be 1 as:

p*x=2*4 = 8

qy=4-28

p*x=q*y=8 which satisfies the condition

Sample Testcase 2

Testcase Input

2 4 1 3

Testcase Output

-1

Give the python code that passes all the test cases