#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Thu Dec 11 09:16:27 2025

@author: pjoulaud
"""

class Noeud:
    def __init__(self, etiquette):
        self.e = etiquette
        self.fils = []
    def ajoute_un_fils(self, noeud):
        self.fils.append(noeud)
    def __str__(self):
        if self.fils :
            chaine = "\n"
            for f in self.fils :
                chaine = chaine + " " + f.__str__()
            return self.e + chaine
        return self.e

n1, n2, n3, n4 = Noeud("1"), Noeud("2"), Noeud("3"), Noeud("4")
n1.ajoute_un_fils(n2)
n1.ajoute_un_fils(n3)
n2.ajoute_un_fils(n4)
print(n1)