def fib(a,b,n):

  if n==0:
    data[0]=a
    return data[0]
  if n==1:
    data[1]=b
    return data[1]
  if data[n]!=-1:
    return data[n]

  data[n]=fib(a,b,n-1)^fib(a,b,n-2)
  return fib(a,b,n-1)^fib(a,b,n-2)

a,b,n = map(int,input().split())
data=[-1]*(n+1)
ans=fib(a,b,n)
print(ans)