f0,f1,n = map(int,input().split())

a = [f1,f0]
i = 1

while True:
	if n == 0:
		a[0] == f0
		break
	if i >= n:
		break
	f = a[0] ^ a[1]
	a[0] , a[1] = f , a[0]
	
	i += 1
	
print(a[0])