Plural formula for Sängö language

In Sängö language, plural marker is handled as follows:

item 0                   ex.:  zo  "person" (general value, can be 
singular or plural)
item 1                   ex.  zo 1 (singular)
items 2 / item 2      ex.  âzo 2  (plural) but also "zo 2" since the 
number 2 already  implies a plural value. So, if 0 stands for the 
unmarked (singular) form and 1 for the marked plural form, the rules may be:

n == 1 ? 0 :  (n == 0 ? 0 : 1)

This formula doesn't make room for the possibility of using the unmarked 
form when a plural value is already implied by a qualifying number or 
any other quantifier, but this is not a hindrance. I hope that this 
formula is correct, if not, please, let me know.

Sincerley yours,

Marcel Diki-Kidiri