#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;

const int NMAX = 100005;

vector<int> g[NMAX], sol;
int grad[NMAX], viz[NMAX], st[NMAX], vf[NMAX], cnt;

void dfs(int nod) {
    st[nod] = ++cnt;
    for (int i = 0; i < g[nod].size(); i++) {
        int vecin = g[nod][i];
        if (!viz[vecin]) {
            viz[vecin] = 1;
            dfs(vecin);
        }
    }
    vf[nod] = cnt;
}

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

    int n, m;
    cin >> n >> m;

    for (int i = 1; i <= m; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }

    bool ok = true;
    for (int i = 1; i <= n; i++) {
        if (grad[i] % 2 == 1) {
            ok = false;
        }
    }

    if (!ok) {
        cout << -1;
        return 0;
    }

    dfs(1);

    for (int i = 1; i <= n; i++) {
        if (st[i] > st[1] && st[i] < vf[1]) {
            ok = false;
        }
    }

    if (!ok) {
        cout << -1;
        return 0;
    }

    vector<int> p;
    p.push_back(1);

    while (p.size() < m + 1) {
        int nod = p.back();
        for (int i = 0; i < g[nod].size(); i++) {
            int vecin = g[nod][i];
            if (g[nod][i] != -1) {
                p.push_back(vecin);
                g[nod][i] = -1;
                break;
            }
        }
    }

    for (int i = 0; i < m; i++) {
        cout << p[i] << " ";
    }

    return 0;
}