##### Short Problem Definition:

Consider a string, s, consisting only of the letters `a`

and `b`

. We say that string s is balanced if both of the following conditions are satisfied:

- s has the same number of occurrences of
`a`

and`b`

. - In each prefix of s, the number of occurrences of
`a`

and`b`

differ by*at most*1.

Your task is to write a regular expression accepting only balanced strings.

##### Link

##### Execution:

Substrings can differ by at most 1 which means that the string must consist of either “ab” or “ba”. Write a regex as such.

##### Solution:

```
Regex_Pattern = r"^((ab)|(ba))*$" # Do not delete 'r'.
```

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