#include <fstream>
#include <stack>
#include <vector>
#include <algorithm>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int NMAX = 100000;
vector <int>g[NMAX+5];
stack <int>st;
bool viz[NMAX+5];

///UN GRAF EULERIAN
///pornind dintr-un nod traversam toate muchiile o singura data si revenim in nodul din care am plecat(prin muchii pot trece o singura data)
///Conditii necesare ca un graf sa fie eulerian
///1) graul e conex
///2)toate gradele nodurilor sunt pare

void dfs(int nod)
{
   viz[nod] = 1;
   for(int i =0;i<g[nod].size();i++)
   {
      if(viz[g[nod][i]] == 0)
        dfs(g[nod][i]);
   }
}
void euler(int nod)
{
   int other;
   while(!g[nod].empty())
   {
      st.push(nod);
      other = g[nod].back();
      g[nod].pop_back();
      g[other].erase(find(g[other].begin(), g[other].end(), nod));
      nod = other;
   }
}
 int main()
{
    int n, m, i, x, y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
       fin>>x>>y;
       g[x].push_back(y);
       g[y].push_back(x);
    }
    dfs(1);
    for(i=1;i<=n;i++)
    {
        if(viz[i]==0 || g[i].size() % 2 == 1)
        {
           fout<<"-1";
           return 0;
        }
    }
    int nod =1;
    ///Am verificat daca graful nostru respecta conditiile necesare
    do{
        euler(nod);
        nod = st.top();
        fout<<nod<<" ";
        st.pop();

    }while(!st.empty());
    return 0;
}