#include <bits/stdc++.h>
#define Nmax 100005
#define Mmax 500005

using namespace std;

int st[Mmax],dr[Mmax],sol[Nmax],N;
bool viz[Mmax],vizz[Nmax];
vector <int> L[Nmax];

inline void Dfss(int nod)
{
    vizz[nod]=true;
    vector <int>:: iterator it;
    for(it=L[nod].begin();it!=L[nod].end();++it)
        if(!vizz[st[*it]+dr[*it]-nod])
            Dfss(st[*it]+dr[*it]-nod);
}

inline bool Conex()
{
    Dfss(1);
    for(int i=1;i<=N;++i)
        if(!vizz[i])
            return false;
    return true;
}

inline bool Este_Euler()
{
    if(!Conex())
        return false;
    for(int i=1;i<=N;++i)
        if(L[i].size()&1)
            return false;
    return true;
}

inline void Dfs(int nod)
{
    vector <int>::iterator it;
    for(it=L[nod].begin();it!=L[nod].end();++it)
        if(!viz[*it])
        {
            viz[*it]=true;
            Dfs(st[*it]+dr[*it]-nod);
        }
    sol[++sol[0]]=nod;
}

int main()
{
    int M,i;
    ifstream f ("ciclueuler.in");
    ofstream g ("ciclueuler.out");
    f >> N >> M;
    for(i=1;i<=M;++i)
    {
        f >> st[i] >> dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
    if(!Este_Euler())
        printf("-1\n");
    else
    {
        Dfs(1);
        for(i=1;i<sol[0];++i)
            g << sol[i] << " ";
    }
    return 0;
}