#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
using namespace std;

#define pb push_back
#define nrmax 100001

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

int n , m , x , y ;
vector < int > G[nrmax];
vector < int > sol;
int grad[nrmax];
bool used[nrmax];

void dfs ( int i )
{
    used[i] = true;
    for ( vector < int > ::iterator j = G[i].begin(); j != G[i].end() ; j++ )
        if (!used[(*j)])
            dfs((*j));
}

void citire ( )
{
    f >> n >> m ;
    for ( ; m-- ; )
    {
        f >> x >> y ;
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
}

void ciclu_euler ( )
{
    int x , alfa;
    stack < int > st;
    st.push(1);
    while(!st.empty())
    {
        x = st.top();
        if ( !G[x].empty() )
        {
            alfa = G[x][0];
            st.push(alfa);
            G[x].erase(G[x].begin());
            G[alfa].erase ( find ( G[alfa].begin() , G[alfa].end() , x )) ;
        }
        else
        {
            sol.push_back(x);
            st.pop();
        }
    }
}

void rezolva()
{
    dfs(1);
    for (int i = 1 ; i <= n ; i++ )
        if ( !used[i] or grad[i]%2 == 1 )
        {
            g << -1;
            return;
        }
    ciclu_euler();
    for ( int i = sol.size()-1 ; i > 0 ; i-- )
        g << sol[i] << " " ;
}


int main()
{
    citire();
    rezolva();
    return 0;
}