#include <iostream>
#include <fstream>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <fstream>


using namespace std;

 ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int NLIM = 1e5 + 10;

int N, M;
int cnt = 0;

vector< int > graph[NLIM];
vector< int > al[NLIM];


int check( int nod )
{
    for( int j = 0; j < graph[nod].size(); ++j )
        if( al[nod][j] )
            return j;
    return -1;
}

void removeEdge( int nod, int j )
{
    //++cnt;
   // if( cnt % 10000 == 0 ) cout << cnt << "\n";
    int nnod = graph[nod][j];
    graph[nod].erase( graph[nod].begin() + j );
    for( int jj = 0; jj < graph[nnod].size(); ++jj )
        if( graph[nnod][jj] == nod )
        {
            graph[nnod].erase( graph[nnod].begin() + jj );
            return;
        }
}

int main()
{
    fin >> N >> M;
    for( int i = 0; i < M; ++i )
    {
        int x, y;
        fin >> x >> y;
        graph[x].push_back( y );
        graph[y].push_back( x );
        al[x].push_back( 1 );
        al[y].push_back( 1 );
    }
    for( int i = 1; i <= N; ++i )
        if( graph[i].size() % 2 != 0 )
        {
            fout << "-1";
            return 0;
        }


    list< int > res;
    res.push_back( 1 );

    list< int >::iterator it;
    for( it = res.begin(); it != res.end(); ++it )
    {

        // check for non traversed edge
       // int edge = check( *it );

        if( graph[*it].size() )
        {
            // get cycle
            queue< int > cic;
            int cur = graph[*it][0];
            removeEdge( *it, 0 );
            cic.push( cur );
            while( cur != *it )
            {
                /*/
                cout << *it << " " <<  cur << "\n";
                for( int h = 1; h <= 3; ++h )
                {
                    cout << "   " << h << ": ";
                    for( int k = 0; k < graph[h].size(); ++k )
                        cout << graph[h][k] << " ";
                    cout << "\n";
                }
                //*/
                int l = cur;
                cur = graph[cur][0];
                removeEdge( l, 0 );
                //res.insert( it, cur );
                cic.push( cur );
            }
            //cout << "end\n";

            list< int >::iterator it2 = it;
            ++it2;
            while( cic.size() )
            {
                res.insert( it2, cic.front() );
                cic.pop();
            }
        }
    }


    for( it = res.begin(); it != res.end(); ++it )
    {
        list< int >::iterator it2 = it;
        ++it2;
        if( it2 != res.end() )
            fout << *it << " ";
    }


    return 0;
}