1:      1  1 CALL pred negation.main/2-0 (det) negation.m:17
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> break p
 0: + stop  interface pred negation.p/2-0 (det)
mdb> continue
       2:      2  2 CALL pred negation.p/2-0 (det) negation.m:25 (negation.m:18)
mdb> finish
      31:      2  2 EXIT pred negation.p/2-0 (det) negation.m:25 (negation.m:18)
mdb> dd -d 3 -n 7
p(1, 42)
Valid? no
r(1, 11)
Valid? yes
q(11)
Valid? yes
r(1, 21)
Valid? yes
q(21)
Valid? yes
Call r(1, _)
Solutions:
	r(1, 11)
	r(1, 21)
Complete? yes
Found incorrect contour:
p(1, 42)
Is this a bug? yes
      31:      2  2 EXIT pred negation.p/2-0 (det) negation.m:25 (negation.m:18)
mdb> continue
42