Description

Assume that the Earth's renewable resources grow at a constant rate. Based on this calculation, the existing resources plus the new resources on Earth can support $x$ billion people for $a$ years, or $y$ billion people for $b$ years.
To achieve sustainable development and avoid resource depletion, what is the maximum number of billion people that Earth can support?

Input Format

Input consists of a single line with four positive integers $x$, $a$, $y$, and $b$, separated by spaces. The constraints are $x > y$, $a < b$, $ax < by$, and each integer is not greater than $10000$.

Output Format

Output a real number $z$, representing the maximum number of billion people that Earth can support, rounded to two decimal places.

Sample

110 90 90 210

75.00