Four Circles

Four circles are mutually tangent to one another as shown in the diagram. If the radiuses of the three larger circles are a, b and c, what is the radius of the fourth circle?

Input

Single line contains three integers: a, b, c – the radiuses of the larger circles (1 ≤ a, b, c ≤ 1000).

Output

Output the radius (one real number accurate to 4 digits after decimal point) of the fourth, the smallest, circle.

Examples