Musical Instrument:
Context: 
Musical Instrument works on frequencies. 
A good Musical play is a one in which each note always emits frequencies which are never the
same. For simplicity we will assume frequencies to be the counts. 
For eg: 
{sa, re sa, ga,ma, ma, pa, ma}
Sa is repeated 2 times
Re -> 1 times
Ga -> 1 times
Ma -> 3 times. 
The above example is not a Good play, because the frequencies emitted are 2,1,1,3 (1 is repeated
two times). To make it a good play, we have to the frequencies unique. 
 
How  to  make it as a good play ?
For example: Remove 3 “Ma” and 1 “Re” (or “Ga”) . This becomes a good Musical play.But,  Number
of removals is 2.
OR
if I remove 1 “Ga” . Then each is repeated uniquely which aren't the same.  Number of removals  is 1.
Minimum  is min (2,1) = 1
 
Problem Stmnt
So given an array , you have to return the minimum number of removals needed to have unique
frequencies. 
For example
S = [aaabbbcc] 
1) You can delete 2 'b's resulting in the good string "aaabcc".  Total: 2 
2) Another way is to delete 1 'b' and 1 'c' resulting in the good string "aaabbc". Total: 2
Output: min (2,2) ~ 2
S= [abcabc]
You can delete 2 of either a, b , c and decrement the other by 1 (remove 2-a and 1-b) minimum
removals is min (2+1) =  3
Either remove 2a OR 2b OR 2c and decrement the rest by 1. So total is 3.
S = ["bbcebab"]
Output: 2
1 <= s < 10^5
S contains LowerCase letters only.