15 - Median

I'm getting an error like so:

```
Traceback (most recent call last):
File "python", line 24, in <module>
File "python", line 13, in median
IndexError: list index out of range
```

Line 13 is:`med = (l[one] + l[two]) / 2.0`

I would think it would work, but I just can't figure it out.

```
def median(numbers):
#first sort the numbers in order
l = sorted(numbers)
#variable to store the median
med = 0
#even number of numbers or odd?
if len(l) % 2 == 0: #even
one = l[len(l) / 2]
two = l[len(l) / 2 - 1]
med = (l[one] + l[two]) / 2.0
print one, two, med
return med
else: #odd
med = l[len(l) / 2]
return med
numbers = [4,5,5,4]
median(numbers)
```