# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	F0, F1, N = getlist()
	if N % 3 == 0:
		print(F0)
	elif N % 3 == 1:
		print(F1)
	else:
		print(F1 ^ F0)



if __name__ == '__main__':
	main()