mother(trude, sally).

father(tom, sally).
father(tom, erica).
father(mike, tom).

sibling(X, Y) :- parent(Z, X), parent(Z, Y).

parent(X, Y) :- father(X, Y).
parent(X, Y) :- mother(X, Y).

` ` ` ` s ` ` s ` k s ` ` s ` k `
 s i ` ` s ` k k ` ` s ` k ` ` s`
` s ` k s ` ` s ` k ` s ` k s ` s
` k k ` ` s ` ` s ` k s ` ` s` k`
s ` k s ` s ` k k ` k ` k i ` ` s
` k ` ` s ` ` s ` ` s i ` k .* `k
r i   i ` k i   i ` d ` ` s ` ` s
` k s ` ` s ` k ` s i ` ` s ` k k
` ` s ` k ` ` s ` ` s ` k s ` ` s
` k ` s ` k s ` s ` k k ` ` s ` `
s ` k s ` ` s ` k ` s ` k s ` s `
k k ` k ` k i ` ` s ` k ` ` s ` `
s ` ` s i ` k .* ` k r i i ` k i

public class MathUtils {

  public boolean isPrime(int n) {
    for (int i=2; i*i<=n; i++) {
      if (n%i==0) {
        return true;
      }
    }
    return false;
  }

}