Easy to understand... but... this solution runs 59 ms, only beats 12% python submissions. Which part takes extra time ?? Thanks

```
def compareVersion(self, version1, version2):
l1 = [int(x) for x in version1.split('.')]
l2 = [int(x) for x in version2.split('.')]
if len(l1) < len(l2):
l1.extend([0]*(len(l2)-len(l1)))
if len(l1) > len(l2):
l2.extend([0]*(len(l1)-len(l2)))
i = 0
while i < len(l1):
if l1[i] > l2[i]:
return 1
elif l1[i] < l2[i]:
return -1
else:
i += 1
return 0
```