Problem: A Christmas party in city S. had n children. All children came in mittens. The mittens can be of different colors, but each child had the left and the right mitten of the same color. Let's say that the colors of the mittens are numbered with integers from 1 to m, and the children are numbered from 1 to n. Then the i-th child has both mittens of color ci.

The Party had Santa Claus ('Father Frost' in Russian), his granddaughter Snow Girl, the children danced around the richly decorated Christmas tree. In fact, everything was so bright and diverse that the children wanted to wear mittens of distinct colors. The children decided to swap the mittens so that each of them got one left and one right mitten in the end, and these two mittens were of distinct colors. All mittens are of the same size and fit all the children.

The children started exchanging the mittens haphazardly, but they couldn't reach the situation when each child has a pair of mittens of distinct colors. Vasily Petrov, the dad of one of the children, noted that in the general case the children's idea may turn out impossible. Besides, he is a mathematician and he came up with such scheme of distributing mittens that the number of children that have distinct-colored mittens was maximum. You task is to repeat his discovery. Note that the left and right mittens are different: each child must end up with one left and one right mitten.

Input

The first line contains two integers n and m — the number of the children and the number of possible mitten colors (1 ≤ n ≤ 5000, 1 ≤ m ≤ 100). The second line contains n integers c1, c2, ... cn, where ci is the color of the mittens of the i-th child (1 ≤ ci ≤ m).

Output

In the first line, print the maximum number of children who can end up with a distinct-colored pair of mittens. In the next n lines print the way the mittens can be distributed in this case. On the i-th of these lines print two space-separated integers: the color of the left and the color of the right mitten the i-th child will get. If there are multiple solutions, you can print any of them.

Examples

Input

6 3
1 3 2 2 1 1


Output

6
2 1
1 2
2 1
1 3
1 2
3 1


Input

4 2
1 2 1 1


Output

2
1 2
1 1
2 1
1 1

Solution (in JAVA):

Solution:
import java.io.*;
import java.util.*;

/**
 * @author pvasilyev
 * @since 07 Dec 2013
 */
public class C {

    public static final String FILE_IN = "std.in";
    public static final String FILE_OUT = "std.out";
    private static boolean debugMode = true;

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

        final Scanner reader = new Scanner(new InputStreamReader(debugMode ? System.in : new FileInputStream(FILE_IN)));
        final PrintWriter writer = new PrintWriter(debugMode ? System.out : new FileOutputStream(FILE_OUT));

        solveTheProblem(reader, writer);

        reader.close();
        writer.close();
    }

    private static void solveTheProblem(final Scanner reader, final PrintWriter writer) {
        final int n = reader.nextInt();
        final int c = reader.nextInt();

        Kid[] pairs = new Kid[n];
        Wrap[] list = new Wrap[c];
        for (int i = 0; i < list.length; i++) {
            list[i] = new Wrap(i + 1, new LinkedList<Integer>());
        }
        for (int i = 0; i < n; i++) {
            final int next = reader.nextInt();
            list[next - 1].list.add(i + 1);
            pairs[i] = new Kid(i + 1, next, next);
        }

        Kid[] kids = new Kid[n];
        int next = 0;

        final PriorityQueue<Wrap> queue = initQueue(c, list);

        while (queue.size() > 0) {
            final Wrap wrap1 = queue.poll();
            kids[next++] = pairs[wrap1.list.pollFirst() - 1];
            if (queue.size() > 0) {
                final Wrap wrap2 = queue.poll();
                kids[next++] = pairs[wrap2.list.pollFirst() - 1];
                if (wrap2.list.size() > 0) {
                    queue.add(wrap2);
                }
            }
            if (wrap1.list.size() > 0) {
                queue.add(wrap1);
            }
        }

        doCycleShift(n, kids);

        Arrays.sort(kids, new Comparator<Kid>() {
            @Override
            public int compare(final Kid o1, final Kid o2) {
                return Integer.compare(o1.id, o2.id);
            }
        });

        int count = countDistinctGloves(kids);

        writeAnswer(writer, pairs, count);
    }

    private static void doCycleShift(final int n, final Kid[] kids) {
        for (int i = 0; i < kids.length - 1; i++) {
            kids[i].right = kids[i + 1].left;
        }
        kids[n - 1].right = kids[0].left;
    }

    private static int countDistinctGloves(final Kid[] kids) {
        int count = 0;
        for (int i = 0; i < kids.length; i++) {
            if (kids[i].left != kids[i].right) {
                count++;
            }

        }
        return count;
    }

    private static void writeAnswer(final PrintWriter writer, final Kid[] pairs, final int count) {
        final StringBuilder builder = new StringBuilder();
        builder.append(count);
        builder.append("\n");
        for (int i = 0; i < pairs.length; i++) {
            Kid pair = pairs[i];
            builder.append(pair.left).append(" ").append(pair.right).append("\n");
        }
        writer.print(builder.toString());
    }

    private static PriorityQueue<Wrap> initQueue(final int c, final Wrap[] list) {
        final PriorityQueue<Wrap> queue = new PriorityQueue<>(c, new Comparator<Wrap>() {
            @Override
            public int compare(final Wrap o1, final Wrap o2) {
                final int compare = Integer.compare(o2.list.size(), o1.list.size());
                final int compare2 = o1.initSize == o2.initSize ? Integer.compare(o1.color, o2.color) : Integer.compare(o2.initSize, o1.initSize);
                return compare == 0 ? compare2 : compare;
            }
        });
        for (int i = 0; i < list.length; i++) {
            if (list[i].list.size() > 0) {
                list[i].initSize = list[i].list.size();
                queue.add(list[i]);
            }

        }
        return queue;
    }

    private static final class Kid {
        int id;
        int left;
        int right;

        private Kid(final int id, final int left, final int right) {
            this.id = id;
            this.left = left;
            this.right = right;
        }
    }

    private static final class Wrap {
        int initSize;
        int color;
        LinkedList<Integer> list;

        private Wrap(final int color, final LinkedList<Integer> list) {
            this.color = color;
            this.list = list;
        }
    }
}