#include <iostream>

 #include <cmath>

 #include <algorithm>

 #include <bitset>

 #include <cstring>

 #include <list>

 using namespace std;

 struct Child{

     int color, num, mat;

 };

 bool partition_cmp(const Child& c1, const Child& c2){

     return c1.color < c2.color;

 }

 bool sort_cmp(const Child& c1, const Child& c2){

     return c1.num < c2.num;

 }

 int main(){

     int n, m;

     Child a[];

     int c[];

     cin >> n >> m;

     for (int i = ; i <= m; i++){

         c[i] = ;

     }

     for (int i = ; i < n; i++){

         cin >> a[i].color;

         a[i].num = i;

         c[a[i].color]++;

     }

     int mx = ;

     for (int i = ; i <= m; i++){

         if (c[mx] < c[i]){

             mx = i;

         }

     }

     if (c[mx] *  > n){

         cout <<  * (n - c[mx]) << endl;

         int mcount = , miter = -, d = n - c[mx];

         for (int i = ; i < n; i++){

             if (a[i].color == mx){

                 cout << a[i].color << " ";

                 if (d > ){

                     for (miter++; miter < n && a[miter].color == mx; miter++);

                     cout << a[miter].color << endl;

                     d--;

                 }

                 else{

                     cout << a[i].color << endl;

                 }

             }

             else{

                 cout << a[i].color << " " << mx << endl;

             }

         }

     }

     else{

         cout << n << endl;

         sort(a, a + n, partition_cmp);

         for (int i = ; i < n; i++){

             a[i].mat = a[(i + c[mx]) % n].color;

         }

         sort(a, a + n, sort_cmp);

         for (int i = ; i < n; i++){

             cout << a[i].color << " " << a[i].mat << endl;

         }

     }

     return ;

 }