import sys

F0,F1,N=map(int,input().split())

if N==0:
 print(F0)
 sys.exit()

elif N==1:
 print(F1)
 sys.exit()
 
for i in range(N-1):
 F=F1^F0 
 F0=F1
 F1=F
 
print(F1)