#include <fstream>
#include <iostream>
#include <algorithm>
#include <list>

using namespace std;

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

list <int> ls[100005];
int n, m, x, y, i;
int stiva[500005], vf;

int main() {
    f >> n >> m;
    while (m--) {
        f >>  x >> y;
        ls[x].push_back(y);
        ls[y].push_back(x);
    }
    for (i = 1; i <= n; i++)
        if (ls[i].size()%2 == 1) {
            g<<-1;
            return 0;
        }
    stiva[vf=1] = 1;
    while (vf > 0) {
        x = stiva[vf];
        cout<<1;
        while (ls[x].size() > 0) {
            y = ls[x].front();
            ls[x].pop_front();
            ls[y].erase( find(ls[y].begin(), ls[y].end(), x) );
            stiva[++vf] = y;
            x = y;
        }
        g << stiva[vf--]<<' ';
    }
    return 0;
}