#!/usr/bin/python

import math
a = int(input())
b = int(input())
c = int(input())
desks = 0

nums = [a,b,c]
for x in nums:
	if x % 2 == 0:
		desks += int(x/2)
	else:
		desks += int(math.floor(x/2) + 1)

print desks