Output issue

[twinpiques]

So, I'm trying a simple "else if" and I am getting the correct output, however, it's also outputting "None".
What am I doing wrong here?

Thank you in advance.

def intro( name, age):
    if name != "" and age > 0:
        print (name, "was born in",2018 - age)
    elif (name == "" or age < 0):
        return ("invalid input")
    else:
        pass

print(intro("Brady",42))

Output:

Output:
Brady was born in 1976
None