If Engage 18.x version and 19.x version running on same machine, do we need 2 different license files or can we use same license file for both the versions? How same license will be uploaded in both versions?

If Engage 18.x version and 19.x version running on same machine, do we need 2 different license files or can we use same license file for both the versions? How same license will be uploaded in both versions?