fact: Definition pred_strong2 (n:nat)(h:2<=n):{v:nat | n = S (S v)} := match pred_strong n (le_2_n_not_zero n h) with | exist _ p h' => match pred_strong p (pred_strong2_th1 n p h h') with | exist _ p' h'' => exist (fun x:nat => n = S (S x)) p' (pred_th1 n p p' h' h'') end end.
imports: ZArith List Arith Lia Zwf