... либо ..., либо ... Третьего не дано.
I assume this is an equivalent of the English expression "it can only go one of two ways" оr "(there's) no in-between".
I'm not sure how to parse the phrase, though, especially the word "дано". My assumptions:
Subject = impersonal, omitted, something like "it" or "the (current) situation"
"дано" = alternative form (?) of "дало", which is the neuter singular past tense of the verb "дать"
"третьего" = direct object of the transitive verb "дать", and in genitive case because of the negative construction
(It / The situation) didn't give/allow a third course/choice.