from collections import defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue,copy,time
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))
def inpl_str(): return list(sys.stdin.readline().split())

X,Y,Z = inpl()
X,Y = min(X,Y), max(X,Y)

if Y - X < Z:
    print((X+Y+Z)//2)
else:
    print(Y+Z)