How to tell Postgres to sort results by the first matching column?

Question

PostgreSQL

Good day dear!
There is a query like: SELECT 1 AS a, 2 AS a ORDER BY a. In which there are two columns named "a". When trying to execute it, it gets "... 'a' is ambigous ..." when sorted. Can you please tell me how to force the result to be sorted by the first column in the results?
PS Yes, I understand that it would be more correct to create an alias, specify a table.column , and so on, but the question is that we have two columns with the same name, and we need to sort by the first one (by the first column with the name "a ", and not on the first column at all).