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:

• $C = \frac{A-B}{3} +B$.

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}.

Constraints

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

Sample Input 1

130 100

Sample Output 1

110

We have $C = \frac{130-100}{3} +100 = 10 + 100 = 110$.

Sample Input 2

300 50

Sample Output 2

133.3333333

Note that although all the values in input are integers, the value to output may not be an integer.

Sample Input 3

123 123

Sample Output 3

123

见题面 Input 部分

见题面 Output 部分