When an initiative proposal and an alternative proposal are put to the vote on the same day, what choices does the voter have?

Law 26300 on the Citizens’ Rights of Participation and Control(Ley 26300 de los derechos de participaci?n y control ciudadanos),

http://aceproject.org/ero-en/regions/americas/PE/peru-ley-de-los-derechos-de-participacion-y/view