x,y,z=map(int,input().split())
ans=0
s=abs(y-x)
if abs(x-y)<z:
    if x<y:
        x+=s
        z-=s
    elif y<x:
        y+=s
        z-=s
else:
    if x<y:
        x+=z
        z=0
    elif y<x:
        y+=z
        z=0

print((x+y)//2+z//2)