Considering One Password

Hey all, Like the title says I'm considering getting one password. But i do have a question about it. I know they say it syncs across all of your devices, and i know that it makes you super long secure passwords. So lets say I have it generate a random password for my gmail account. As a student i use public computers in the library a lot. Now if i need to log in to my gmail on a public computer like the one at my university, how do I do this if i do not know my gmail password?