n = [0, 0, 0]
n[0], n[1], n[2] = map(int, input().split())
if min(n) == 0 and max(n) < 3:
    print(0)
else:
    n.sort()
    a = n[1] - n[0]
    b = n[2] - n[0]
    x = int((a + b) / 4) + n[0]
    if a % 2 == 0 and b % 2 == 0:
        x -= 1
    print(x)