a,b,c=map(int,input().split())
d=max(a,b)-min(a,b)
if (d==a or d==b) and c==0: print(0)
elif a+c<b or b+c<a:
    print(min(a+c,b+c))
else: print(max(c-d,0)//2+max(a,b))