mf0,mf1,n = gets.chomp.split(" ").map(&:to_i)
f0 = mf0
f1 = mf1  
a = 0
i = 0
p = 0
while(1 <= f0 or 1 <= f1)
if((f0%2+f1%2) == 1)
  a += 2**i
end
  f0 /= 2
  f1 /= 2
  i += 1
end
if(n%3 == 0)
  puts mf0 
elsif(n%3 == 1)
  puts mf1
else
  puts a
end
=begin
88 79 2
=end