def fib_xor1(x,y,n,rec):
	if n==0:
		rec[0] = x
		return x
	elif n == 1:
		rec[1] = y
		return y
	elif n in rec:
		return rec[n]
	else:
		rec[n] = fib_xor1(x,y,n-1,rec)^fib_xor1(x,y,n-2,rec)
		return rec[n]

x,y,n = map(int,input().split(" "))
rec = {}
print(fib_xor1(x,y,n,rec))