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

x,y,n = map(int,input().split(" "))
print(fib_xor(x,y,n))