I didn't know this, did you?
A twice-before-elected President may become Vice-President either through appointment or through election and — like any other Vice-President — may thereafter succeed from that office to the Presidency for the full remainder of the pending term.
https://digitalcommons.law.uga.edu/fac_artchop/1012/#:~:text=In%20fact%2C%20the%20relevant%20constitutional,that%20office%20to%20the%20Presidency