A = list(map(int, input().split()))

def check(X):
	return sum((x - X) // (2 if x >= X else 1) for x in A) >= 0

ok, ng = 0, max(A) + 1
while ng - ok > 1:
	mid = (ok + ng) // 2
	if check(mid):
		ok = mid
	else:
		ng = mid

print(ok)