public static void addSign(Arena arena, Sign sign){
		if(sign != null){
			ArrayList<Sign> arenaSigns = new ArrayList<Sign>();
			if(signs.get(arena) != null){
				arenaSigns = signs.get(arena);
				if(signs.get(arena).contains(sign)) return;
			}
			arenaSigns.add(sign);
			signs.put(arena, arenaSigns);

			File fichier_signs = new File(OneInTheChamber.instance.getDataFolder() + File.separator + "Signs.yml");
			YamlConfiguration signsFile = YamlConfiguration.loadConfiguration(fichier_signs);

			List<String> locsArenaSign = new ArrayList<String>();  

			for(Sign arenaSign : signs.get(arena)){
				String locArenaSign = LocationManager.locToString(arenaSign.getLocation());
				locsArenaSign.add(locArenaSign);
			}

			signsFile.set("Arenas." + arena.getName() + ".Signs", locsArenaSign);

			try {
				signsFile.save(fichier_signs);
			} catch (IOException e) {
				e.printStackTrace();
			}
		}

	}