#include <bits/stdc++.h>
using namespace std;
 
string longestPalindrome(string str){
	map<char,int> frequencyChar;
	for(int i=0;i<str.length();i++){
		frequencyChar[str[i]]++;
	}
	char middle_character='\0';
	string leftStr;
	for(auto it: frequencyChar){
		char currentChar=it.first;
		int frequencyCurrentChr = it.second;
		if(frequencyCurrentChr%2!=0){
			middle_character=min(currentChar,middle_character);
		}
		leftStr.append(frequencyCurrentChr/2,currentChar);
	}
	string rightStr(leftStr.rbegin(),leftStr.rend());
	return leftStr + middle_character + rightStr;
}
int main() {
	string str = "adskassda";
	cout<<longestPalindrome(str);
}

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