Given a string, rearrange it in such a way that it has no subsequence as cba. If there are multiple answers return the lexicographically smallest one.
Example 1:
Input:
N=6
S="aaaaab"
Output:
aaaaab
Explanation: "aaaaab" has no subsequence as cba and is
lexicographically the smallest one.
Example 2:
Input:
N=3
S="cba"
Output:
abc.
Explanation: "abc" has no subsequence as cba and is
lexicographically the smallest one.

Your Task:
You don't need to read input or print anything. Your task is to complete the function cbaSubsequence() which takes the string S, its size N as input parameters and returns the rearranged string.

Expected Time Complexity: O(NLogN)
Expected Auxiliary Space: O(1)

Constraints:
1<=N<=10^{5}
S contains only lowercase English alphabets.

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