#include <bits/stdc++.h>
using namespace std;
//aproapeperm
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int n, m;
int X[500005], Y[500005], viz[500005], d[100005], p[100005];
vector<int> L[100005], sol;

bool ToatePare()
{
    for (int i = 1; i <= n; i++)
        if (d[i] % 2 == 1) return false;
    return true;
}
void Euler(int k)
{
    while (p[k] < L[k].size())
    {
        int i = L[k][p[k]++];
        if (viz[i] == 0)
        {
            viz[i] = 1;
            Euler(X[i] + Y[i] - k);
        }
    }
    sol.push_back(k);
}

int main()
{
    int i, j, k;
    fin >> n >> m;
    for (k = 1; k <= m; k++)
    {
        fin >> i >> j;
        d[i]++; d[j]++;
        L[i].push_back(k);
        L[j].push_back(k);
        X[k] = i; Y[k] = j;
    }
    if (ToatePare() != true) fout << "-1\n";
    else
    {
        Euler(1);
        sol.pop_back();
        for (int i : sol)
            fout << i << " ";
        fout << "\n";
    }
    return 0;
}