#include <fstream>
#include <vector>
#include <bitset>
using namespace std;
const int NMAX = 100001;
const int MMAX = 500001;

struct muchie {
    int nod, nrm;
    muchie(int xx = 0, int nn = 0) : nod(xx), nrm(nn) {}
};

int n, m;
vector<muchie> G[NMAX];
vector<int> L;
bitset<MMAX> elim;

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

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

void euler(int x) {
    muchie mm;
    while (!G[x].empty()) {
        mm = G[x].back();
        G[x].pop_back();
        if (!elim[mm.nrm])
        {
            elim[mm.nrm] = 1;
            euler(mm.nod);
        }
    }
    L.push_back(x);
}

int main() {
    bool ok = 1;
    citire();
    for (int i = 1; i <= n && ok; i++) {
        if (G[i].size() % 2 == 1) {
            ok = 0;
        }
    }
    if (ok) {
        euler(1);
        for (int i = L.size() - 1; i >= 0; i--) {
            g << L[i] << ' ';
        }
    }
    else {
        g << "-1\n";
    }

    f.close();
    g.close();
    return 0;
}