domino

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

class lab04
{

    public static void licz(int ile, Domino[] dom)
    {
    int[] kropki = new int[7];
    for (int i=0; i<ile; i++)
        {
        kropki[dom[i].getLeft()]++;
        kropki[dom[i].getRight()]++;
        }
    int licz_niep=0;
    int niep1=-1;
    int niep2=-1;
    for (int i=0; i<7; i++)
        {
        licz_niep+=kropki[i]%2;
        if (kropki[i]%2==1)
            if (niep1==-1) niep1=i;
            else niep2=i;

    //  System.out.println("Kropek "+i+" jest: "+kropki[i]);
        }
    //System.out.println("Liczb nieparzystych jest: "+licz_niep);
    if (licz_niep==2)
        if (czy_istnieje(dom, niep1, niep2, ile))
            System.out.println("NIE");
        else
            {
            System.out.println(niep1+" "+niep2);
            }
    else
        System.out.println("NIE");
    }
////////////////////////////////////////////////////////////////////////////
    public static boolean czy_istnieje(Domino[] dom, int n1, int n2, int size)
    {
    for(int i=0; i<size; i++)
        {
        if ((dom[i].getLeft()==n1) && (dom[i].getRight()==n2) ) return true;
        if (dom[i].getLeft()==n2 && dom[i].getRight()==n1) return true;
        }
    return false;
    }
////////////////////////////////////////////////////////////////////////////
    public static void main (String[] args)
    {
    System.out.println("Wejście:");
    Scanner in = new Scanner(System.in);
    int n = in.nextInt();
    Domino[] d= new Domino[n];
    for(int i=0; i<n; i++)
        {
        int x = in.nextInt();
        int y = in.nextInt();
        d[i]=new Domino (x,y);
        }
    //int y = in.nextInt();
    //System.out.println(x+"+"+y+"="+(x+y));
    /*int n=5;
        Domino[] d= new Domino[n];
        d[0]=new Domino (1,2);
        d[1]=new Domino (2,3);
        d[2]=new Domino (5,4);
        d[3]=new Domino (3,6);
        d[4]=new Domino (6,4);*/
    //for (int i=0; i<n; i++)
    //  d[i].print();
    System.out.println();
    System.out.println("Wynik:");
    if (n==1) System.out.println(d[0].getLeft()+" "+d[0].getRight());
    else licz(n, d);




    }
//////////////////////////////////////////////////////////////
    public static class Domino
    {
    private int _left;
    private int _right;
    public Domino(int left, int right)
    {
    _left=left;
    _right=right;
    }

    int getLeft(){ return _left;}
    int getRight(){ return _right;}
    void print()
        {
        System.out.print("("+getLeft()+" "+getRight()+")");
        }


    }


}