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

using namespace std ;

ifstream f ("ciclueuler.in") ;
ofstream g ("ciclueuler.out") ;

int N, M;
vector <int> Viz, Deg;
list <int> G[100005], L;
stack <int> S;

void dfs(int nod)
{
    Viz[nod] = 1 ;
    for (const int & x : G[nod])
        if (Viz[x] == 0)
            dfs (x) ;
}

int conex ()
{
    dfs ( 1 ) ;
    for (int cnt = 1; cnt <= N; ++cnt)
    if (Viz[cnt] == 0)
        return 0 ;
    return 1;
}


int euler ()
{
    if ( conex () == 0 )
        return 0;
    for (int cnt = 1; cnt <= N; ++cnt)
        if (Deg[cnt] % 2 == 1)
            return 0;
    return 1;
}

void sterge(int v, int w)
{
    --Deg[v], --Deg[w];
    G[v].pop_front();
    for (list <int> :: iterator it = G[w].begin(); it != G[w].end(); ++it)
        if(*it == v)
        {
             G[w].erase(it);
             break ;
        }
}

void euler(int v)
{
    while(true)
    {
        if(G[v].empty())
            break ;
        int w = G[v].front();
        S.push(v);
        sterge(v, w);
        v = w;
    }
}

void cauta_ciclu_eulerian()
{
    int nod = 1;
    L.push_back(nod);
    do  {
          euler(nod) ;
          nod = S.top() ;
          S.pop();
          L.push_back(nod);
        }while (!S.empty());
    L.pop_back();
    for (const int & x : L)
        g << x << " ";
}

int main ()
{
    f >> N >> M;
    Viz = vector <int> (N + 1);
    Deg = vector <int> (N + 1);
    for ( int cnt = 1 ; cnt <= M ; ++cnt )
    {
        int x , y ;
        f >> x >> y ;
        G[x].push_back (y);
        G[y].push_back (x);
        ++Deg[x], ++Deg[y];
    }
    if (euler() == 0)
        g << "-1";
    else
        cauta_ciclu_eulerian ();
    f.close();
    g.close();
    return 0;
}