Yes, 'the'... and a comma after digit. You cannot omit 'the' when 'first' is serving as an adjective for a countable noun or is a pronoun acting in lieu thereof.
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Clive I drank a second cup of coffee. non-specific reference.
Clive
Hi
I know you either put "the" or nothing, but I think I've never heard about putting "a" before second, third etc.