I need help in Lesson 3 I do not understand and I can not go ...

I need urgent help

def square():

"""Retorna o quadrado de um numero."""

squared = n**2

print "%d squared is %d." % (n, squared)

return squared

def square(10):

"""Retorna o quadrado de um numero."""

squared = 10**2

print "%d squared is %d." % (10, squared)

return squared

what is wrong here?