See the original problem on HackerRank.
Solutions
Let’s call l
the length of the string. Thus, we have copies = n / l
copies of the string.
Let’s call occ
the number of occurrences of a
in the string. Thus, we have at least occ * l
occurrences of a
.
The extra number of a
is calculated from the possible remainder of the first n / l
characters in the string. So we calculate the number of a
in the first n%l
characters.
Here is a C++ solution:


An alternative solution in Python:


Possible perturbations:
 don’t use the module operator