\includegraphics{https://static.e-olymp.com/content/b6/b688da921ccd1cfe6288e01d8903e8f1c36a7cfc.jpg} Four circles are mutually tangent to one another as shown in the diagram. If the radiuses of the three larger circles are \textbf{a}, \textbf{b} and \textbf{c}, what is the radius of the fourth circle? \InputFile Single line contains three integers: \textbf{a}, \textbf{b}, \textbf{c} -- the radiuses of the larger circles (\textbf{1} ≤ \textbf{a}, \textbf{b}, \textbf{c} ≤ \textbf{1000}). \OutputFile Output the radius (one real number accurate to \textbf{4} digits after decimal point) of the fourth, the smallest, circle.