# The Butterfly – Medical Attendan

When pupils are going from home to school or from school to home they like to eat candies. But, as usual, this pleasant matter sometimes has unpleasant consequences. They sometimes throw out wrappings on a school yard .

Murzyk always watched after the cleanness of school yard and butterflies helped him with gladness. The butterflies were thankful to him for wonderful pictures. Butterflies could use own porches as lenses, thus they could change their focal distance. When they notice a wrapping from a candy which lays on a school yard in a point with the coordinates X1, Y1, a butterfly flitted to the a point with the coordinates X2, Y2, Z2, which located on the way of sunbeam to wrapping and they changing focal distance of the porches-lenses and then burned wrapping from a candy.

What optical force of `D`

did the porches-lenses of butterfly have at this moment?

## Input

In the first line is 2 numbers: coordinates X1, Y1 of wrapping from a candy. In the second line – 3 numbers: coordinates X2, Y2, Z2 of butterfly in the moment of incineration of wrapping.

All of entrance information are integers which do not exceed 1000 by the module.

## Output

There is one number which equal to the optical force of porches-lenses `D`

, which calculated within 3 signs after point by the rules of the mathematical rounding.