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 $*b*$ ($|*a*|, |*b*| ≤ 10^{9}$), the elements of the first row of matrix $*A*$.

The second line contains two integers $*c*$ and $*d*$ ($|*c*|, |*d*| ≤ 10^{9}$) 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 $10^{ - 9}$.

Note

In the first sample matrix $*B*$ is

In the second sample matrix $*B*$ is