Proc Optmodel constraint help

[SAScowboy]

Could someone help me figure out how to add a constraint that requires at least one of adwords 3,5,7 to be bought? 

Also how to force the model to never buy adword 35?

Thank you in advance!

proc optmodel;
set ADWORDS = 1..100;
num cost_per_click{ADWORDS} = ranuni(123);
num clicks{ADWORDS} = ranuni(567);
num conversions{ADWORDS} = ranuni(789);
num revperconversion=10;
var buy{ADWORDS} >=0;
max effectiveness =sum{a in ADWORDS}((revperconversion*conversions[a])-(clicks[a]*cost_per_click[a]))*buy[a];
con buyAtMost50: sum{a in ADWORDS}buy[a]<=50;
con buyAtMostOfEven: sum{a in ADWORDS: mod(a,2) = 0}buy[a]<=10;
con buyAtMostOfOdd: sum{a in ADWORDS: mod(a,1) = 0}buy[a]<=20;
solve;
Quit;

[RobPratt · Accepted solution]

First a correction to your constraint:

con buyAtMostOfOdd: sum{a in ADWORDS: mod(a,2) = 1}buy[a]<=20;

Now here is a way to force 3, 5, 7:

con AtLeastOne357: sum {a in {3,5,7}} buy[a] >= 1;

And here are four alternative ways to avoid 35.

Explicit constraint:

con No35: buy[35] = 0;

Fixed variable:

fix buy[35] = 0;

Change index set declaration:

set ADWORDS = 1..100 diff {35};

Modify index set after declaration:

set ADWORDS init 1..100;
ADWORDS = ADWORDS diff {35};

[SAScowboy]

Thank you again!