type arbre23 = | F of int
| N2 of arbre23 * int * arbre23
| N3 of arbre23 * int * arbre23 * int * arbre23
;;

let agg = N2 (F 8, 8, F 10);;
let agd = N3 (F 15, 17, F 22, 22, F 23);;