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

#define DIM 100005

using namespace std;

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

int grad[DIM], c[DIM], mp[DIM];
int n, nrs, x, y, m, nr;

vector <pair <int, int> > G[DIM];
stack <int> stiva;

void dfs (int node) {
    c[node] = 1;
    for (vector <pair <int, int> > :: iterator it = G[node].begin(); it != G[node].end(); ++it) {
        if (c[it -> first] == 0) {
            dfs (it -> first);
        }
    }
}

void euler () {
    stiva.push (1);
    int ok = 1;

    while (!stiva.empty ()) {
        int node = stiva.top();
        if (grad[node] == 0) {
            if (ok == 0) {
                g << node << " ";
            }

            ok = 0;
            stiva.pop();
        }

        else {
            while (!G[node].empty() && mp[G[node][G[node].size () - 1].second] == 1) {
                G[node].pop_back ();
            }

            if (G[node].empty ())
                continue;

            int v = G[node][G[node].size () - 1].first;
            int aux = G[node][G[node].size () - 1].second;
            mp[aux] = 1;

            --grad[node];
            --grad[v];

            stiva.push(v);
        }
    }
}

int main() {
    f >> n >> m;
    for (int i = 1; i <= m; ++i) {
        f >> x >> y;
        G[x].push_back ({y, ++nr});
        G[y].push_back ({x, nr});

        ++grad[x];
        ++grad[y];
    }

    for (int i = 1; i <= n; ++i) {
        if (grad[i] % 2 == 1) {
            g << -1;
            return 0;
        }
    }

    dfs (1);
    for (int i = 1; i <= n; ++i) {
        if (c[i] == 0) {
            g << -1;
            return 0;
        }
    }

    euler ();
    return 0;
}