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

using namespace std;

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

const int N=100005;
const int M=500005;

int n, m, viz[M], q[M], k, sol[M];
vector <pair <int, int> > a[N];

void dfs(int i)
{
    int j, v;
    while (!a[i].empty())
    {
        j=a[i].back().second;
        v=a[i].back().first;
        a[i].pop_back();
        if (!viz[j])
        {
            viz[j]=1;
            dfs(a[i].back().first);
        }
    }
    k++;
    sol[k]=i;
}
int main()
{
    int i, x, y;

    f>>n>>m;
    for (i=1; i<=m; i++)
    {
        f>>x>>y;
        a[x].push_back(make_pair(y, i));
        a[y].push_back(make_pair(x, i));
    }

    // verific daca are gradul par
    for (i=1; i<=n; i++)
      if (a[i].size() % 2 == 1) { cout<<-1; return 0; }

    dfs(1);

    for (i=1; i<=k; i++) cout<<sol[i]<<" ";
    return 0;
}