How many persons are needed to call robbery a dacoity?

Section 391 of the Indian Penal Code provides that when five or more persons conjointly commit or attempt to commit a robbery or where the whole number of persons conjointly committing or attempting to commit a robbery and persons present and aiding such commission or attempt, amount to five or more, every person so committing, attempting or aiding, is said to commit the offence of dacoity.