%%HP: T(3)A(R)F(.);
\<< FACTORS 1
  \<<
    IF NSUB 2 MOD
    THEN FACTORS 1
      \<<
        IF NSUB 2 MOD
NOT
        THEN XQ ^
\->CPAIR
        END
      \>> DOSUBS
      IF DUP SIZE 1
==
      THEN HEAD
      ELSE \PILIST
      END
    END
    IF NSUB 2 MOD NOT
    THEN XQ
    END
  \>> DOSUBS
  IF DUP SIZE 1 ==
  THEN HEAD
  ELSE \PILIST
  END
\>>