public class QuickF {
    public static void main (String [] args) {
	int N = Integer.parseInt (args[0]);
	Out.println ("N = " + N);
	int id[] = new int[N];
	for (int i = 0; i < N; i++) id[i] = i;
	for (In.init (); !In.empty (); /*none*/) {
	    int p = In.getInt (), q = In.getInt ();
	    int t = id[p];
	    if (t == id[q]) continue;
	    for (int i = 0; i < N; i++)
		if (id[i] == t) id[i] = id[q];
	    Out.println (" " + p + " " + q);
	}
    }
}