The Butterfly – Medical Attendant#57
Schoolchildren, on their way from home to school or vice versa, enjoy eating candies. However, as is often the case, this pleasant habit sometimes leads to unpleasant consequences — children often throw candy wrappers in the schoolyard.
Smugastyk always kept the schoolyard clean, and butterflies, grateful for the beautiful photographs Smugastyk took, gladly helped him. Butterflies could use their wings as lenses and adjust their focal length at will. When a butterfly spotted a candy wrapper at the point with coordinates X_1, Y_1 in the schoolyard, it would fly to the point with coordinates X_2, Y_2, Z_2 — along the path of a sunbeam that reaches the wrapper — adjust the focal length of its wing-lenses, and burn the candy wrapper.
What was the optical power of the butterfly's wing-lenses at that moment?
The first line contains two integers: the coordinates X_1, Y_1 of the candy wrapper.
The second line contains three integers: the coordinates X_2, Y_2, Z_2 of the butterfly at the moment of burning the wrapper.
All input numbers are integers with absolute value not exceeding .
Output a single number — the optical power of the wing-lenses, rounded mathematically to three decimal places.
Example 1