// prob.cpp - C++ code for solving problem 5

#include <stdio.h>
#include <iostream.h>

// Uncomment the following lines if using APCS classes
#include "apvector.h"
#include "apmatrix.h"
#include "apstack.h"
// #include "apqueue.h"
// #include "apstring.cpp"


bool Ham(int num, 
		 apmatrix<bool> &adj, 
		 apstack<int> &seats, 
		 apvector<bool> &marked)
{
	int i, j = seats.top();

	if (num == seats.length() && adj[j][0]) {
		return true;
	}

	for (i=1; i<num; i++) {
		if (!marked[i] && adj[j][i]) {
			marked[i] = true;
			seats.push(i);
			if (Ham(num, adj, seats, marked))
				return true;
			else {
				seats.pop();
				marked[i] = false;
			}
		}
	}
	return false;
}

int main()
{
	int num;            // number of diplomats to be seated
	int i,x,y;

	// read in problem description

	cin >> num;
	apmatrix<bool> adj(num,num,true); // who's allowed to be adjacent

 
	for (i=0; i<num; i++)  // can't sit next to oneself
		adj[i][i] = false;

	while (true) {
		cin >> x;
		if (x == -1)
			break;
		cin >> y;
		adj[x-1][y-1] = false; // can't sit next to each other
		adj[y-1][x-1] = false;
	}

	// find seating

	apstack<int> seats;               // seats for diplomats
	apvector<bool> marked(num,false); // which nodes visited

	seats.push(0);
	if (Ham(num, adj, seats, marked)) {
		while (!seats.isEmpty()) {
			seats.pop(x);
			cout << x+1 << " ";
		}
		cout << "\n";
	}
	else {
		cout << "0" << "\n";
	}

	return 0;
}