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

using namespace std;

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

const int N = 1e5;
int grad[N + 1];

bool viz[N * 5 + 1];

struct muchie
{
    int nod, nr_muchie;
};

vector <muchie> g[N + 1];

int n, m, x, y;

vector <int> sol;

stack <int> s;

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= m; ++i)
    {
        cin >> x >> y;
        g[x].push_back({y, i});
        g[y].push_back({x, i});
        grad[x]++;
        grad[y]++;
    }
    for (int i = 1; i <= n; ++i)
        if (grad[i] & 1)
        {
            cout << "-1\n";
            return 0;
        }
    for (int i = 1; i <= n; ++i)
        if (!g[i].empty())
        {
            s.push(i);
            break;
        }
    while (!s.empty())
    {
        int node = s.top();
        if (!g[node].empty())
        {
            int nod = g[node].back().nod;
            int m = g[node].back().nr_muchie;
            g[node].pop_back();
            if (!viz[m])
                viz[m] = 1, s.push(nod);
        }
        else
            sol.push_back(node), s.pop();
    }
    sol.erase (sol.end() - 1);
    for (auto it : sol)
        cout << it << ' ';
    return 0;
}