URI Online Judge | 1156

S Sequence II

Adapted by Neilor Tonin, URI Brazil

Timelimit: 1

Write an algorithm to calculate and write the value of S, S being given by:
S = 1 + 3/2 + 5/4 + 7/8 + ... + 39/?

Input

There is no input in this problem.

Output

The output contains a value corresponding to the value of S.
The value should be printed with two digits after the decimal point.

Input Sample Output Sample