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

using namespace std;

ifstream in ("ciclueuler.in");
ofstream out ("ciclueuler.out");

vector< vector<int> >g(100010);
vector<int> st;
vector<int> ans;
struct muchii
{
    int dus,ins;
} v[500010];
bool used[500010];
int grad[100010];

int main()
{
    int n,i,j,x,y,nd,e,m;
    in>>n>>m;
    for(i=1; i<=m; i++)
    {
        in>>x>>y;
        g[x].push_back(i);
        g[y].push_back(i);
        v[i].dus=x;
        v[i].ins=y;
        grad[x]++;
        grad[y]++;
    }
    for(i=1; i<=n; i++)
        if(grad[i]%2==1)
        {
            out<<"-1";
            return 0;
        }
    st.push_back(1);
    while(!st.empty())
    {
        nd=st.back();
        if(!g[nd].empty())
        {
            e=g[nd].back();
            g[nd].pop_back();
            if(used[e]==false)
            {
                used[e]=true;
                if(v[e].ins==nd)
                    st.push_back(v[e].dus);
                else
                    st.push_back(v[e].ins);
            }
        }
        else
        {
            ans.push_back(nd);
            st.pop_back();
        }
    }
    for(i=0; i<ans.size()-1; i++)
        out<<ans[i]<<" ";
    return 0;
}