namespace Sticks
{
    using System;
    using System.Collections.Generic;
    using System.Linq;

    public static class Startup
    {
        private static string HandleInput(Func<string> inputFunc)
        {
            string input = inputFunc.Invoke();

            if (string.IsNullOrEmpty(input) || string.IsNullOrWhiteSpace(input))
            {
                throw new ArgumentException("Input cannot be empty!", "inputFunc");
            }

            return input;
        }

        public static void Main()
        {
            int sticksCount = int.Parse(HandleInput(Console.ReadLine));

            ICollection<int> sticks = new HashSet<int>();

            for (int index = 0; index < sticksCount; index++)
            {
                sticks.Add(index);
            }

            int placings = int.Parse(HandleInput(Console.ReadLine));

            ICollection<int> upperSticks = new HashSet<int>();
            ICollection<int> lowerSticks = new HashSet<int>();

            IDictionary<int, ICollection<int>> lowerSticksByUpperStick = new Dictionary<int, ICollection<int>>();
            IDictionary<int, ICollection<int>> upperSticksByLowerStick = new Dictionary<int, ICollection<int>>();

            for (int i = 0; i < placings; i++)
            {
                string input = HandleInput(Console.ReadLine);
                string[] inputArgs = input.Split(new[] {' '}, StringSplitOptions.RemoveEmptyEntries);

                int upperStick = int.Parse(inputArgs[0]);
                int lowerStick = int.Parse(inputArgs[1]);

                upperSticks.Add(upperStick);
                lowerSticks.Add(lowerStick);

                if (lowerSticksByUpperStick.ContainsKey(upperStick))
                {
                    lowerSticksByUpperStick[upperStick].Add(lowerStick);
                }
                else
                {
                    lowerSticksByUpperStick[upperStick] = new HashSet<int> { lowerStick };
                }

                if (upperSticksByLowerStick.ContainsKey(lowerStick))
                {
                    upperSticksByLowerStick[lowerStick].Add(upperStick);
                }
                else
                {
                    upperSticksByLowerStick[lowerStick] = new HashSet<int> { upperStick };
                }
            }

            ICollection<int> upmostSticks = GetUpmostSticks(sticks, upperSticks, lowerSticks, new HashSet<int>());
            ICollection<int> usedSticks = new HashSet<int>();

            while (upmostSticks.Any())
            {
                // take the upmost stick
                int upmostStick = upmostSticks.FirstOrDefault();

                // remove it
                upperSticks.Remove(upmostStick);

                if (lowerSticksByUpperStick.ContainsKey(upmostStick))
                {
                    ICollection<int> lowerSticksCollection = lowerSticksByUpperStick[upmostStick];

                    foreach (int stick in lowerSticksCollection)
                    {
                        upperSticksByLowerStick[stick].Remove(upmostStick);

                        if (!upperSticksByLowerStick[stick].Any())
                        {
                            lowerSticks.Remove(stick);
                        }
                    }

                    lowerSticksByUpperStick.Remove(upmostStick);
                }

                // mark as used
                usedSticks.Add(upmostStick);

                upmostSticks = GetUpmostSticks(sticks, upperSticks, lowerSticks, usedSticks);
            }

            if (usedSticks.Count == sticks.Count)
            {
                Console.WriteLine(string.Join(" ", usedSticks));
            }
            else
            {
                Console.WriteLine("Cannot lift all sticks\n{0}", string.Join(" ", usedSticks));
            }
        }

        private static ICollection<int> GetUpmostSticks(
            ICollection<int> sticks, ICollection<int> upperSticks, ICollection<int> lowerSticks, ICollection<int> usedSticks)
        {
            var resultingStack = new Stack<int>();

            foreach (int stick in sticks)
            {
                if (upperSticks.Contains(stick) && !lowerSticks.Contains(stick) ||
                    !upperSticks.Contains(stick) && !lowerSticks.Contains(stick) && !usedSticks.Contains(stick))
                {
                    resultingStack.Push(stick);
                }
            }

            var result = new HashSet<int>();

            while (resultingStack.Any())
            {
                result.Add(resultingStack.Pop());
            }

            return result;
        }
    }
}