import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;
import java.io.PrintStream;

/** Program to read a sequences of words and print all words in it that
 *  appear more than once.
 *  @author P. N. Hilfinger
 */
public class Dups1 {

    /** Read the sequence of words on INPUT, and return as a List.  If LINKED,
     *  use a linked representation.  Otherwise, use an array representation.
     */
    static List<String> readList(Scanner input, boolean linked) {
        List<String> L;
        if (linked) {
            L = new LinkedList<String>();
        } else {
            L = new ArrayList<String>();
        }
        while (input.hasNext()) {
            L.add(input.next());
        }
        return L;
    }

    /** Return a list of all items in L that appear more than once.
     *  Each item appears once in the result.
     */
    static List<String> duplicates(List<String> L) {
        ArrayList<String> result = new ArrayList<String>();
        for (int i = 0; i < L.size(); i += 1) {
            String x = L.get(i);
            if (result.contains(x)) {
                continue;
            }
            for (int j = i + 1; j < L.size(); j += 1) {
                if (x.equals(L.get(j))) {
                    result.add(x);
                    break;
                }
            }
        }
        return result;
    }


    /** Print the items in L on OUTPUT on a line, separated by blanks. */
    static void writeList(List<String> L, PrintStream output) {
        for (int k = 0; k < L.size(); k += 1) {
            output.printf("%s ", L.get(k));
        }
        output.println();
    }

    /** Read words from the standard input and print the list of duplicated
     *  words.  Internally use a linked representation for the input list
     *  iff ARGS[0] is "linked". */
    public static void main(String... args) {
        boolean useLinked = args.length == 0 || args[0].equals("linked");
        writeList(duplicates(readList(new Scanner(System.in), useLinked)),
                   System.out);
    }

}