# Degenerate Matrix

Time Limit: 1 second

Memory Limit: 256 megabytes

## Description

The determinant of a matrix 2 × 2 is defined as follows: A matrix is called degenerate if its determinant is equal to zero.

The norm ||A|| of a matrix A is defined as a maximum of absolute values of its elements.

You are given a matrix . Consider any degenerate matrix B such that norm ||A - B|| is minimum possible. Determine ||A - B||.

## Input

The first line contains two integers a and b (|a|, |b| ≤ 109), the elements of the first row of matrix A.

The second line contains two integers c and d (|c|, |d| ≤ 109) the elements of the second row of matrix A.

## Output

Output a single real number, the minimum possible value of ||A - B||. Your answer is considered to be correct if its absolute or relative error does not exceed 10 - 9.

## Sample Input

Input1 23 4Output0.2000000000Input1 00 1Output0.5000000000

## Sample Output

None

## Hint

In the first sample matrix B is In the second sample matrix B is None