The number of chocolates that Alice is losing per day is \(D1\). Whereas, the number of chocolates that Bob is gaining per day is \(D2\). Currently, the number of chocolates that Alice and Bob contains is \(A\) and \(B\) respectively.

You are required to calculate the number of chocolates that Alice has when Bob does not contain any chocolates. 

Note

• In any case, Alice always loses all the chocolates.
• \(A\%D1=0\)

Input format

The first and only line contains four space-separated integers \(A\), \(B\), \(D1\), and \(D2\).

Output format

Print a single integer denoting the number of chocolates that Bob contains.

Note: It is guaranteed that the answer always exists.

Constraints

\(1\le A,\ B \le10^3\\ 1\le D1,\ D2\le10^3\\ 1\le D1\le A\)