## Day of the week that is K days later

Given a string `S`, returns the maximum number of letters `a` that can be inserted into `S` (including at the front and end of `S`) so that the resulting string doesn’t contain three consecutive letters `a`. If string `S` already contains the substring `aaa`, then your function should return `-1`.

### Example 1:

#### Explanation:

A string `aabaabaa` can be made

### Example 2:

#### Explanation:

A string `aadaaoaagaa` can be made

### Example 3:

#### Explanation:

No longer string can be made.

### Example 4:

#### Explanation:

There is a substring `aaa`

## Implementation

 `1` `1` ``from itertools import groupby`` `2` `2` ``def maxInserts(s):`` `3` `-` `` # WRITE YOUR BRILLIANT CODE HERE`` `3` `+` `` ans, last = 0, '#'`` `4` `+` `` for c, g in groupby(s):`` `5` `+` `` L = len(list(g))`` `6` `+` `` if c == 'a':`` `7` `+` `` if L < 3:`` `8` `+` `` ans += 2 - L`` `9` `+` `` else:`` `10` `+` `` return -1`` `11` `+` `` else:`` `12` `+` `` ans += 2 * (L - (last == 'a'))`` `13` `+` `` last = c`` `14` `+` `` ans += 2 * (s[-1] != 'a')`` `15` `+` `` return ans`` `16` `+` `4` `17` ``if __name__ == '__main__':`` `5` `18` `` print(maxInserts(input()))``