sunny.                   /* It is sunny. */
father(john, peter).     /* John is the father of Peter. */
father(john, mary).
father(david, liza).
father(david, john).
father(jack, susan).
father(jack, ray).
mother(susan, peter).    /* Susan is the mother of Peter. */
mother(susan, mary).
mother(amy, liza).
mother(amy, john).
mother(karen, susan).
mother(karen, ray).
loves(john, susan).      /* John loves Susan. */
b1([p, 2, q], p).        /* No special meaning. */

yeye(X, Y) :- father(X, Temp), father(Temp, Y).
        /* X is the "yeye" of Y if X is the father of Temp and Temp is the father of Y. */
mama(X, Y) :- mother(X, Temp), father(Temp, Y).
gunggung(X, Y) :- father(X, Temp), mother(Temp, Y).
popo(X, Y) :- mother(X, Temp), mother(Temp, Y).
a(A1, [A | B]) :- A1 is A + 1.
a(A, [B | C]) :- a(A, C).