public class UF

{

    private int[] id;

    private int count;

    public UF(int N)

    {

        count=N;

        id=new int[N];

        for (int i=0;i<N;i++)

            id[i]=i;

    }

   

     public int count()

     {return count;}

    

      boolean connected(int p,int q)

      {return find(p)==find(q);}

      /*quick-find

       public int find(int p)

       {return id[p];}

      

       public  void union(int p,int q)

       {

          int pID=find(p);

          int qID=find(q);

          if (pID==qID) return;

          for (int i=0;i<id.length;i++)

              if(id[i]==pID) id[i]=qID;

          count--;

       }

       */

      public int find(int p)

      {

          while(p!=id[p]) p=id[p];

          return p;

      }

     

      public void union(int p,int q)

      {

          int pRoot=find(p);

          int qRoot=find(q);

          if(pRoot==qRoot) return;

          id[pRoot]=qRoot;

          count--;

      }

      

       public static void main(String[] qrgs)

       {

           int N=StdIn.readInt();

           UF uf=new UF(N);

           while (!StdIn.isEmpty())

           {

               int p=StdIn.readInt();

               int q=StdIn.readInt();

               if(uf.connected(p,q)) continue;

               uf.union(p,q);

               StdOut.println(p+ " " +q);

            }//end while

        }//end main

}//end class