1:      1  1 CALL pred backtrack.main/2-0 (det) backtrack.m:17
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> break p
 0: + stop  interface pred backtrack.p/2-0 (det)
mdb> continue
       2:      2  2 CALL pred backtrack.p/2-0 (det) backtrack.m:24 (backtrack.m:18)
mdb> finish
      23:      2  2 EXIT pred backtrack.p/2-0 (det) backtrack.m:24 (backtrack.m:18)
mdb> dd -d 3 -n 7
p(1, no)
Valid? no
q(1, 1)
Valid? yes
Call >(1, 5)
Unsatisfiable? yes
q(1, 2)
Valid? yes
Call >(2, 5)
Unsatisfiable? yes
q(1, 3)
Valid? yes
Call >(3, 5)
Unsatisfiable? yes
Call q(1, _)
Solutions:
	q(1, 1)
	q(1, 2)
	q(1, 3)
Complete? yes
Found incorrect contour:
p(1, no)
Is this a bug? yes
      23:      2  2 EXIT pred backtrack.p/2-0 (det) backtrack.m:24 (backtrack.m:18)
mdb> continue
no