SETINT: Perform a set intersection operation on two positive integer sets
SETINT(A,B,C), will assign to set A: B n C,
n: denotes set intersection

syntax: SETINT(target_letter, set_letter1, set_letter2)

Performs a set intersection operation on the sets with the letter variable <set_letter1> and <set_letter2> which refers to letter variable ($A...$Z) then puts the results from the set intersection operation into <target_letter> set.