The program calculates the value of the expression
\(ans = {2 + \sqrt{2} \over {5 + \sqrt{5}}} + {5 + \sqrt{5} \over {13 + \sqrt {13}}}+{13 + \sqrt{13} \over {8 + \sqrt{8}}}\).
For calculation, the drop(a, b) function is used, which calculates the value of one term.
Write the missing line in this function.