def urbanmain() = {

  import C1._

  assert(collatz_max(10) == (19, 9))
  assert(collatz_max(100) == (118, 97))
  assert(collatz_max(1000) == (178, 871))
  assert(collatz_max(10000) == (261, 6171))
  assert(collatz_max(100000) == (350, 77031))
  assert(collatz_max(1000000) == (524, 837799))
}