#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");
int n,m,poz;
int x,y;
struct muchie{
    int next;
    int nr;
};
vector<vector<muchie>> A;
vector<bool> fr;
vector<int> Gr;
stack<int> S;
void dfs(int nod)
{
    for(int i=0;i<A[nod].size();i++)
    {
        int vecin=A[nod][i].next;
        int numar=A[nod][i].nr;
        if(!fr[numar])
        {
            fr[numar]=1;
            dfs(vecin);
        }
    }
    S.push(nod);
}
int main()
{
    cin>>n>>m;
    A.resize(n+1);
    fr.resize(m);
    Gr.resize(n+1);
    for(int i=0;i<m;i++)
    {
        cin>>x>>y;
        A[x].push_back({y,i});
        A[y].push_back({x,i});
        Gr[x]++;
        Gr[y]++;
    }
    for(int i=n;i>=1;i--)
      if(Gr[i]%2)
        {
            cout<<-1;
            return 0;
        }
       else
         if(Gr[i])
           poz=i;
    dfs(poz);
    while(!S.empty())
    {
        if(S.size()>1)
        cout<<S.top()<<" ";
        S.pop();
    }
    return 0;
}