Goal:
  
  A : Type
  l : list A
  x : A
  cstr : BinInt.Z.le BinNums.Z0 (BinInt.Z.of_nat #|l|)
  ============================
   (BinInt.Z.of_nat #|l| =
    BinInt.Z.max BinNums.Z0
      (BinInt.Z.sub
         (BinInt.Z.add (BinInt.Z.of_nat #|l|) (BinNums.Zpos BinNums.xH))
         (BinNums.Zpos BinNums.xH)))


DEBUG:Going to execute:
fun => <coq-core.plugins.zify::ITER@0>