def I():return int(input())
def MAP():return map(int,input().split())
def MAPs():return map(str,input().split())
def LI(): return list(map(int,input().split()))
def TPL(): return tuple(map(int,input().split()))
def S():return input()
from collections import defaultdict,Counter,deque
from copy import deepcopy
from heapq import heapify,heappop,heappush
from bisect import bisect_left,bisect_right
from itertools import accumulate,product,permutations,combinations
from math import gcd,ceil,floor,sqrt
inf=float('inf');mod=998244353;Mod=10**9+7

f0,f1,n=MAP()
if n%3==0:
    print(f0)
elif n%3==1:
    print(f1)
else:
    print(f0^f1)