X,Y,Z = map(int,input().split())

if Z==0:
    print(min(X,Y))
else:
    if X<Y:
        if Y-X>=Z:
            print(X+Z)
        else:
            Z-=(Y-X)
            print(Y+Z//2)
    elif X>Y:
        if X-Y>=Z:
            print(Y+Z)
        else:
            Z-=(X-Y)
            print(X+Z//2)
    else:
        print(X+Z//2)