Oops, try again. median([4, 5, 5, 4]) returned 4 instead of 4.5

The sorted list is [4,4,5,5] and I am retrieving values from the sorted list. What is wrong with my code?

```
def median(first_list):
second_list=sorted(first_list)
length=len(first_list)
if length%2==0:
return (second_list[(length/2)-1]+second_list[(length/2)])/2
else:
return second_list[((length+1)/2)-1]
```