#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
#define MAXN 100010
#define MAXM 500010

typedef vector <int> :: iterator iter;
vector <int> G[MAXN];
int viz[MAXN], d[MAXN], st[MAXM];


void df(int nod)
{
    viz[nod] = 1;
    for(iter it = G[nod].begin() ; it != G[nod].end() ; it++)
    {
        if(!viz[*it])
            df(*it);
    }
}
int main()
{
    int n, m, x, y, ok, i, dr, nod, v;
    fin >> n >> m;
    while(m--)
    {
        fin >> x >> y;
        d[x]++;
        d[y]++;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    ok = 1;
    for(i = 1 ; i <= n ; i++)
        if(d[i] % 2 == 1)
            ok = 0;
    df(1);
    for(i = 1 ; i <= n ; i++)
        if(!viz[i])
            ok = 0;
    if(ok == 0)
    {
        fout << "-1\n";
        return 0;
    }
    dr = 0;
    st[++dr] = 1;
    while(dr)
    {
        nod = st[dr];
        if(G[nod].size())
        {
            v = G[nod][G[nod].size() - 1];
            for(iter it = G[v].begin() ; it != G[v].end() ; it++)
                if(*it == nod)
                {
                    G[v].erase(it);
                    break;
                }
            G[nod].pop_back();
            st[++dr] = v;
            continue;
        }
        if(dr != 1)
            fout << nod << " ";
        dr--;
    }
}