Sal de Liema recalls being befriended by Otto Frank, whom he called "Papa Frank," and how together they developed small mental exercises (such as remembering the opening of Beethoven's 9th Symphony which allowed them to keep their sanity amidst the horrors that surrounded them.
Sal de Liema, an inmate at Auschwitz who knew both Otto Frank and Hermann van Pels, said that after two or three days in the camp, van Pels mentally "gave up", which was generally the beginning of the end for any concentration camp inmate.