import math
import sys
def S(): return sys.stdin.readline().rstrip()
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int, sys.stdin.readline().rstrip().split())
def LI(): return list(map(int, sys.stdin.readline().rstrip().split()))
def LS(): return list(sys.stdin.readline().rstrip().split())

f0, f1, n = MI()
f2 = f0^f1
if n%3 == 0:
    print(f0)
elif n%3 == 1:
    print(f1)
elif n%3 == 2:
    print(f2)