a, b, c = io.read("*n", "*n", "*n")
if a == b and b == c then
  print(a)
elseif a ~= b and a ~= c and b ~= c then
  print(6 - a - b - c)
else
  if a == b then
    print(c)
  elseif b == c then
    print(a)
  else
    print(b)
  end
end