In reply to kernalmode1:
The problem with your constraint on cnum is that there is no constraint on any element. The expression
cnum.sum with (int’(item.index<3?1:0)) has a constant value 3. It would easier to do what you want using
and reduction.
cnum.and with (item.index<3?item:!item));
BTW, always test the result of calling randomize().