#include <iostream>
#include <fstream>
#include <algorithm>
#include <queue>
#include <cstring>
#include <vector>
#include <climits>
#include <bitset>
#include <cmath>
#include <climits>
#include <stack>
#include <stdlib.h>
#include <queue>

using namespace std;

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

stack<int> s;
vector<int> x[100001];
int afis[500010];

int main()
{
    int n, m, z = 0;
    f >> n >>m;
    if (m%2==1)
    {

    for (int i = 1; i <= m; i++)
    {
        int a, b;
        f >> a >> b;
            x[a].push_back(b);
            x[b].push_back(a);
    }
    int nod = 1, nod_nou;
    s.push(1);
    while (!s.empty())
    {
        nod = s.top();
        if (!x[nod].empty())
        {
            nod_nou = x[nod].front();
            s.push(nod_nou);
            vector<int>::iterator it;
            it = find(x[nod].begin(), x[nod].end(), nod_nou);
            x[nod].erase(it);
            it = find(x[nod_nou].begin(), x[nod_nou].end(), nod);
            x[nod_nou].erase(it);
        }
        else
        {
            afis[++z] = s.top();
            s.pop();
        }
    }
    for (int i = z; i >= 2; i--)
        g << afis[i] << " ";
    }
    else
        g <<-1;
    return 0;
}