The vowel substrings in the word `codewarriors` are `o,e,a,io`. The longest of these has a length of 2. Given a lowercase string that has alphabetic characters only (both vowels and consonants) and no spaces, return the length of the longest vowel substring.
Vowels are any of `aeiou`. 
```if:csharp
Documentation:
Kata.Solve Method (String)
Returns the length of the greatest continuous vowel substring in a string.
Syntax
public
static
int Solve(
string str
    )
Parameters
str
Type: System.String
The string to be processed.
Return Value
Type: System.Int32
  The length of the greatest continuous vowel substring in str, or 0 if str contains no vowels.
Exceptions
Exception
Condition
ArgumentNullException
str is null.
```
Good luck!
If you like substring Katas, please try:
[Non-even substrings](https://www.codewars.com/kata/59da47fa27ee00a8b90000b4)
[Vowel-consonant lexicon](https://www.codewars.com/kata/59cf8bed1a68b75ffb000026)
def solve(s):
    vowels = 'aeiou'
    max_len = 0
    tmp_len = 0
    prev_vowel = False
    for c in s:
        max_len = max(max_len, tmp_len)
        if not prev_vowel:
            tmp_len = 0
        if c in vowels:
            tmp_len += 1
        prev_vowel = c in vowels
    return max_len
def solve(s):
    vowels = 'aeiou'
    max_len = 0
    tmp_len = 0
    prev_vowel = False
    for c in s:
        max_len = max(max_len, tmp_len)
        if not prev_vowel:
            tmp_len = 0
        if c in vowels:
            tmp_len += 1
        prev_vowel = c in vowels
    return max_len