23 50's In Swim

Every monday and friday I have swim. Yesterday I had swim and we where doing 50's. 2 laps, flip turns at each end. So the teacher said we where doing four 50's free style, but here comes the bad part. Five sets of four 50's. That is twenty 50's, plus three 50's at the very end. 23 50's in swim, it was totally breathtaking, literally I could not breath. Finally, half way on my last one, my 23rd I was so relived that I had reached the end on my 23rd 50.