#include <bits/stdc++.h>

using namespace std;

int n,m,gr[100005],viz[100005];
vector <int > g[100005],sol;
stack <int > st;
void citire()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        g[y].push_back(x);
        gr[x]++;gr[y]++;
    }
}
void dfs(int nod)
{
    viz[nod]=1;
    for (vector <int > :: iterator it=g[nod].begin();it!=g[nod].end();++it)
        if (!viz[*it])
            dfs(*it);
}
int e_conex()
{
    dfs(1);
    for (int i=1;i<=n;++i)
        if (!viz[i])
        return 0;
    return 1;
}
int gr_par()
{
    for (int i=1;i<=n;++i)
        if (gr[i]%2!=0)
        return 0;
    return 1;
}
int adm_euler()
{
    if (e_conex() && gr_par())
        return 1;
    return 0;
}
void parcurg(int v)
{
    while (1)
    {
        if (g[v].empty())
            break;
        int w=g[v].front();
        st.push(v);
        for (vector <int > :: iterator it=g[w].begin();it!=g[w].end();++it)
            if (*it==v)
                {
                    g[w].erase(it);
                    break;
                }
        g[v].erase(g[v].begin());
        v=w;
    }
}
void solve()
{
    int v=1;
    do
    {
        parcurg(v);
        v=st.top();
        st.pop();
        sol.push_back(v);
    }
    while (!st.empty());
    for (vector <int > :: iterator it=sol.begin();it!=sol.end();++it)
        printf("%d ",*it);
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
    if (adm_euler())
    {
        solve();
        return 0;
    }
    printf("-1");
    return 0;
}