#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int n, m, a[100][100], c[100];

void citire () {
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;
        a[x][y] = a[y][x] = 1;
    }
}

void dfs (int nod) {
    c[nod]++;
    for (int i =1; i <= n; i++) {
        if (a[i][nod] == 1 and c[i] == 0)
            dfs(i);
    }
}

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

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

int eulerian () {
    if (!conex())
        return 0;
    for (int i = 1; i <= n; i++) {
        if (grad(i) % 2 == 1)
            return 0;
    }
    return 1;
}

void ciclu (int nod) {
    int maxx = 0, nmax = 0;
    fout << nod << " ";
    for (int i = 1; i <= n; i++) {
        if (a[i][nod] == 1) {
            if (grad(i) > maxx) {
                maxx = grad(i);
                nmax = i;
            }
        }
    }
    if (nmax != 0) {
        a[nod][nmax] = a[nmax][nod] = 0;
        ciclu(nmax);
    }

}

int main () {
    citire();
    if (eulerian()) {
        ciclu(1);
    }
    else {
        fout << -1;
    }
}