Problem:
Handsel

Alice and Brown are brothers in a family and each receives pocket money in celebration of the coming year. They are very close and share the total amount of the money fifty-fifty. The pocket money each receives is a multiple of 1,000 yen.

Write a program to calculate each one’s share given the amount of money Alice and Brown received.

Input

The input is given in the following format.

a b

A line of data is given that contains two values of money: a (1000 ≤ a ≤ 50000) for Alice and b (1000 ≤ b ≤ 50000) for Brown.

Output

Output the amount of money each of Alice and Brown receive in a line.

Sample Input 1

1000 3000

Sample Output 1

2000

Sample Input 2

5000 5000

Sample Output 2

5000

Sample Input 3

1000 2000

Sample Output 3

1500

Solution in PHP (judge verdict: Accepted)

<?php
$input=explode(' ',trim(fgets(STDIN)));
$a=intval($input[0]);
$b=intval($input[1]);
$money=($a+$b)/2;
echo $money;
?>