#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;

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);
    }

    stack<int> nodes;

    nodes.push(1);

    while (!nodes.empty()) {
        int nod = nodes.top();
        if (edges[nod].empty()) {
            nodes.pop();
            ciclu.push_back(nod);
            continue;
        }
        int w = *(edges[nod].begin());
        auto it = edges[nod].begin();
        edges[nod].erase(it);
        it = edges[w].find(nod);
        edges[w].erase(it);
        nodes.push(w);
    }


    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;
}