Definition checkPrfIMP1 (p recs : nat) :=
  let A := cPairPi1 (cPairPi2 (cPairPi2 p)) in
  let B := cPairPi2 (cPairPi2 (cPairPi2 p)) in
  charFunction 2 beq_nat (cPair 1 (cPair A (cPair 1 (cPair B A))))
    (cPairPi1 p).

Lemma checkPrfIMP1IsPR : isPR 2 checkPrfIMP1.