I am a little tight on paper space and I need to write >in one sitting<, or something of the sort, down but >in one sitting< will not fit onto the paper. So I need a single, concise word that has the same definition of in one sitting. Here is a sentence to help. I want to do all of my homework [in one sitting].
Well if it's space and not word count:
I want to do all of my homework in one go.
If you don't mind the added ambiguity (can be taken as "now"):
I want to do all of my homework at once.
If it is the word count and you don't mind sounding like a vocabulary nerd:
I want to do all of my homework contiguously