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:
    for i in range(2):
        for j in range(1, 3):
            if n[i] > n[j]:
                n[i], n[j] = n[j], n[i]
    a = n[1] - n[0]
    b = n[2] - n[0]
    x = int((a + b) / 4) + n[0]
    print(x)