I dont even really fuckin know" mostly pronounced as a phonetic word (ih-durfk) as opposed to saying each letter individually (ai-dee-ee-ar-ef-kay). However, either can be used. In many cases "iderfk" is used in conjunction with "idgaf
Teacher: "Johnny, What is the answer to #9?"
Johnny: "uhmm, c=5"
Teacher: "What theorem does this prove?"
Johnny: "iderfk to be honest with you, and idgaf either"