Deny all but import IP Addresses

Deny all but import IP Addresses

Hey all, I have a need to deny all IP's except those listed. The list is well over 200 IP's. Is there in import feature, or file I can paste these into? I am limited to 1 hour, preferably less maintenance window. I understand it won't apply until I select apply, but the access window stands by security contract. This would also help save time in being less prone to typo errors.