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

I have no idea why this doesn't work, it looks fine to me, help much appreciated

```
def median(x):
x_sort = sorted(x)
if len(x) == 1:
return (x[0])
elif len(x)%2 == 0:
return (x_sort[len(x)/2-1] + x_sort[len(x)/2])/2
else:
return x_sort[round(len(x)/2)]
```