Definition int_eqMixin := CanEqMixin natsum_of_intK.Definition int_countMixin := CanCountMixin natsum_of_intK.Definition int_choiceMixin := CountChoiceMixin int_countMixin.Canonical int_eqType := Eval hnf in EqType int int_eqMixin.Canonical int_choiceType := Eval hnf in ChoiceType int int_choiceMixin.Canonical int_countType := Eval hnf in CountType int int_countMixin.Definition int_rec := int_rect.Definition int_ind := int_rect.

Lemma addSz (m n : int) : (1 + m) + n = 1 + (m + n).