Definition checkPrfIMP2 (p recs : nat) :=
  let A := cPairPi1 (cPairPi2 (cPairPi2 p)) in
  let B := cPairPi1 (cPairPi2 (cPairPi2 (cPairPi2 p))) in
  let C := cPairPi2 (cPairPi2 (cPairPi2 (cPairPi2 p))) in
  charFunction 2 beq_nat
    (cPair 1
       (cPair (cPair 1 (cPair A (cPair 1 (cPair B C))))
          (cPair 1 (cPair (cPair 1 (cPair A B)) (cPair 1 (cPair A C))))))
    (cPairPi1 p).

Lemma checkPrfIMP2IsPR : isPR 2 checkPrfIMP2.