#include <fstream>
#include <vector>
using namespace std;
ifstream cin ("ciclueuler.in");
ofstream cout ("ciclueuler.out");
bool u[500005];
vector < pair<int,int> > g[100005];
int d[100005];
int n,m;
void dfs(int nod)
{
    u[nod] = true;
    for(auto urm:g[nod])
    {
        if(u[urm.first])
            continue;
        dfs(urm.first);
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        cin >> x >> y;
        g[x].push_back({y,i});
        g[y].push_back({x,i});
        d[x]++;
        d[y]++;
    }
    dfs(1);
    for(int i=1;i<=n;i++)
        {
            if(!u[i] || d[i]%2!=0)
            {
                cout << "-1";
                return 0;
            }
        }
    for(int i=1;i<=m;i++)
        u[i] = false;
    vector<int> rasp;
    vector<int> st;
    st.push_back(1);
    while(!st.empty())
    {
        int vf = st.back();
        if(g[vf].empty())
        {
            rasp.push_back(vf);
            st.pop_back();
            continue;
        }
        pair<int,int> much = g[vf].back();
        if(u[much.second])
        {
            g[vf].pop_back();
            continue;
        }
        u[much.second] = true;
        st.push_back(much.first);
        g[vf].pop_back();
    }
    rasp.pop_back();
    for(auto x:rasp)
        cout << x << ' ';
    return 0;
}