a,b,c = map(int,input().split())

S = set([a,b,c])
if len(S) == 1:
	print(a)
elif len(S) == 3:
	print(6-a-b-c)
else:
	li = [a,b,c]
	li.sort()
	if li[0] == li[1]:
		print(li[2])
	else:
		print(li[0])