As far as I know, you must not be in the US for 5 years total (365*5 days). But you must be in the US, for half of the time of 5 years which is 912 days. You shouldn't be out of the US for more than 6 months. The more time you are out, it adds up on 5 years,

For more info, go to USCIS.gov and search, continuous residency, or just google it.

Good luck