Christmas is coming, and Santa has a long list to go through, to find who deserves presents for the big day. Go through a list of children, and return a list containing every child who appeared on Santa's list. Do not add any child more than once. Output should be sorted.
~~~if:java
For java, use Lists.
~~~
Comparison should be case sensitive and the returned list should contain only one copy of each name: `"Sam"` and `"sam"` are different, but `"sAm"` and `"sAm"` are not.
def find_children(a, b):
    return sorted(set(a) & set(b))
def find_children(a, b):
    return sorted(set(a) & set(b))