from heapq import *
from itertools import *
from functools import *
from collections import *
import sys,math
input = sys.stdin.readline

X,Y,Z = map(int,input().split())
X,Y = max(X,Y),min(X,Y)
if Z < X - Y:
    print(Z + Y + Z)
else:
    val = (X+Y+Z)//2
    print(val)