Problem Statement

You are given a person's systolic blood pressure, $A$, and diastolic blood pressure, $B$. Find the mean arterial pressure, $C$, which we define as follows:

• $C = \frac{A-B}{3} +B$.

Constraints

• $50 \leq B \leq A \leq 300$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B

Output

Print the value $C$. Your output is considered correct when its absolute or relative error from our answer is at most $10^{-5}$.