Description

Assume that the renewable resources on Earth grow at a constant rate. According to this calculation, the existing resources plus the newly generated resources can support x billion people living for a years, or y billion people living for b years.
To achieve sustainable development and avoid resource depletion, what is the maximum number of billions of people the Earth can support?

Input Format

One line containing four positive integers x, a, y, b, separated by single spaces. The constraints are: x > y, a < b, ax < by, and each integer does not exceed 10000.

Output Format

A real number z, representing the maximum number of billions of people the Earth can support, rounded to two decimal places.

110 90 90 210

75.00