#include <fstream>
#include <algorithm>
#include <climits>
#include <stack>
#include <vector>
#define ll long long
using namespace std;

const int NMAX = 100000;
stack <int> s;

vector <int> g[NMAX + 1];
vector <int> sol;

int grad[NMAX + 1];
int main()
{
    ifstream cin("ciclueuler.in");
    ofstream cout("ciclueuler.out");
    int n, m, i;
    cin >> n >> m;
    for (i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
        grad[a]++;
        grad[b]++;
    }
    bool ok = 1;
    for (i = 1; i <= n; i++)
        if (grad[i] % 2 == 1)
        {
            ok = 0;
            break;
        }
    if (!ok)
    {
        cout << -1;
        return 0;
    }
    s.push(1);
    while (!s.empty())
    {
        int f = s.top();
        if (!g[f].empty())
        {
            int vecin = g[f].back();
            g[f].pop_back();
            g[vecin].erase(find(g[vecin].begin(), g[vecin].end(), f));
            s.push(vecin);
        }
        else
        {
            sol.push_back(f);
            s.pop();
        }
    }
    for (i = sol.size() - 1; i > 0; i--)
        cout << sol[i] << " ";
}