/* IMPORTANT: Multiple classes and nested static classes are supported */


//imports for BufferedReader

import java.io.BufferedReader;
import java.io.InputStreamReader;

//import for Scanner and other utility classes
import java.util.*;


// Warning: Printing unwanted or ill-formatted data to output will cause the test cases to fail

class TestClass {

    public static void main(String args[]) throws Exception {


//        //BufferedReader
//        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//        String name = br.readLine();                // Reading input from STDIN
//        System.out.println("Hi, " + name + ".");    // Writing output to STDOUT

        //Scanner
        Scanner s = new Scanner(System.in);
        s.nextLine();
        Map<Integer, Integer> frequencyOfNumbers = new TreeMap<>();
        String[] integers = s.nextLine().split(" ");
        Arrays.stream(integers)
                .map(Integer::parseInt)
                .mapToInt(Integer::intValue)
                .forEach(i -> {
                            if (!frequencyOfNumbers.containsKey(i))
                                frequencyOfNumbers.put(i, 1);
                            else {
                                Integer numberOfTimes = frequencyOfNumbers.get(i);
                                    frequencyOfNumbers.remove(i,numberOfTimes);
                                    numberOfTimes+=1;
                                    frequencyOfNumbers.put(i,numberOfTimes);
                            }
                        }
                );
        int sum = frequencyOfNumbers
                .entrySet()
                .stream()
                .filter(en -> en.getValue() % 2 == 0)
                .map(Map.Entry::getKey)
                .mapToInt(Integer::intValue).sum();
        System.out.println(sum);


        // Write your code here

    }
}