#include <iostream>
#include <fstream>
#include <vector>

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

#define limn 100010
#define limm 500010
typedef vector <int> :: iterator iter;
vector <int> G[limn];
int viz[limn], d[limn], st[limm];


void dfs (int nod)
{
    viz[nod]=1;
    for (iter it=G[nod].begin(); it!=G[nod].end(); it++)
        if (!viz[*it])
            dfs (*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;
    dfs (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--;
    }
    return 0;
}