Kindly provide a hint to this problem cant seem to get an idea

#1

Kindly provide any hint . Dont know what to do with K

#2

@achin1tya,
K is the atmost number of character you can change, for e,g in sample input,

Sample Input
4
abba

We can change 1st b->a and 2nd b->a, i.e total number of changes = 2, and the perfectness = {aaaa} = 4.

#3

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