import java.io.*;
import java.util.*;


public class diplomatic
{


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

//Einlesroutine
BufferedReader in = new BufferedReader (new FileReader("diplomatic.in"));
int n = 0;
String s="";
long[] x=new long [0];
long[] y=new long [0];

while(true) {
     String data = in.readLine();
     if (data == null) break;
     StringTokenizer st = new StringTokenizer (data);
     while(st.hasMoreTokens())
           if (n==0) { 
                     s = st.nextToken();
                     if ( s.compareTo("EOF")==0 ) s = "0";
                     Long I= new Long( s );
                     n = I.intValue();
                     x = new long[n];
                     y = new long[n];
                     }
              else {
                   for(int i=0;i<n;i++) {
                      s = st.nextToken();
                      Long I = new Long( s );
                      x[i] = I.intValue();
                      I = new Long( st.nextToken() );
                      y[i] = I.intValue();
                      }
                   }
     if (n!=0) Aufg_D(n,x,y);
     n=0;
     } //while
}


public static void Aufg_D(long n, long[] x, long [] y)
{
System.out.print(n  + " ");
for (int i=0; i<n;i++) {
    if ( i!= x.length-1) {
       System.out.print( ( (x[i]+x[i+1])/2 ) + " " );
       System.out.print( ( (y[i]+y[i+1])/2 ) + " " );
       }
       else {
       System.out.print( ( (x[i]+x[0])/2 ) + " " );
       System.out.print( ( (y[i]+y[0])/2 ) + " " );
       }
    }
System.out.println("");
}






}