Add typing to binary_exponentiation_3.py
diff --git a/maths/binary_exponentiation_3.py b/maths/binary_exponentiation_3.py
index dd4e70e74129..9cd143e09207 100644
--- a/maths/binary_exponentiation_3.py
+++ b/maths/binary_exponentiation_3.py
@@ -11,7 +11,7 @@
 """
 
 
-def b_expo(a, b):
+def b_expo(a: int, b: int) -> int:
     res = 1
     while b > 0:
         if b & 1:
@@ -23,7 +23,7 @@ def b_expo(a, b):
     return res
 
 
-def b_expo_mod(a, b, c):
+def b_expo_mod(a: int, b: int, c: int) -> int:
     res = 1
     while b > 0:
         if b & 1:

### Describe your change:



* [ ] Add an algorithm?
* [ ] Fix a bug or typo in an existing algorithm?
* [x] Documentation change?

### Checklist:
* [x] I have read [CONTRIBUTING.md](https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md).
* [x] This pull request is all my own work -- I have not plagiarized.
* [x] I know that pull requests will not be merged if they fail the automated tests.
* [x] This PR only changes one algorithm file.  To ease review, please open separate PRs for separate algorithms.
* [x] All new Python files are placed inside an existing directory.
* [x] All filenames are in all lowercase characters with no spaces or dashes.
* [x] All functions and variable names follow Python naming conventions.
* [x] All function parameters and return values are annotated with Python [type hints](https://docs.python.org/3/library/typing.html).
* [x] All functions have [doctests](https://docs.python.org/3/library/doctest.html) that pass the automated testing.
* [x] All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
* [x] If this pull request resolves one or more open issues then the description above includes the issue number(s) with a [closing keyword](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue): "Fixes #ISSUE-NUMBER".
