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

t = len(list({a,b,c}))

if t == 1:
	print(a)
elif t == 2:
	if a == b:
		print(c)
	elif b == c:
		print(a)
	elif c == a:
		print(b)
else:
	print(6-a-b-c)