I try to find how many children a person have. Created my sample space and in find procedure i should count the numbers of children and print the value.

sample input/output:

```
?- find(joe,Result).
false.
```

i tried to change `find(X,R)`

like that:

```
find(X,R) :-
R is 0 .
R is R+1 ,
father(X,Y).
write(R).
```

then its input/output became like that

```
?- find(joe,R).
R = 0.
```

I tried what i know about prolog but i think i have few knowledge to do that task. All suggestions are welcome. Thanks for all your interest.

```
:- [library(clpr)].
mother(susan, sue).
father(joe, eric).
father(joe, smith).
father(joe, barrack).
father(sue, john).
father(eric, bill).
father(bill, george).
find(X,R):-
R is 0,
R is R+1 ,
father(X,Y).
```