Number of chocolates
95% Success2443 Attempts10 Points1s Time Limit256MB Memory1024 KB Max Code

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

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

Examples
Input
100 10 5 100
Output
2010
Explanation

Initially, Mr. A has 100 chocolates and Mr.B has 10 chocolates and it is given that Mr.A is losing 5 chocolates per day so it will take 20 days from today to become poor and in these 20 days Mr.B  will gain 100*20 =2000 chocolates so Mr.B chocolates become 2010.

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