#include <iostream>
#include <queue>
#include <fstream>
#include <map>
#include <set>
#include <cstring>
#include <stack>
#include <ctime>
#include <cstdlib>
#define N_MAX 100005
#define MOD 666013
using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
int n, m;
multiset<int> edges[N_MAX];
vector<int> ciclu;

void euler(int nod) {
    while (!edges[nod].empty()) {
        int w = *(edges[nod].begin());
        cout << w << endl;
        auto it = edges[nod].begin();
        edges[nod].erase(it);
        it = edges[w].find(nod);
        edges[w].erase(it);
        euler(w);
    }
    ciclu.push_back(nod);
}

int main()
{
    in >> n >> m;
    int x, y;
    for (int i = 1; i <= m; i++) {
        in >> x >> y;
        edges[x].insert(y);
        edges[y].insert(x);
    }
    euler(1);
    for (int i = 1; i <= n; i++) {
        if (!edges[i].empty()) {
            out << -1;
            return 0;
        }
    }

    for (int i = 0; i < ciclu.size() - 1;i++) {
        out << ciclu[i] << ' ';
    }

    return 0;
}