//solutie cu o stiva si cu stiva sistem
#include <fstream>
#include <vector>
#include <set>
using namespace std;
const int NMAX = 100001;

multiset <int> g[NMAX];
vector <int> sol;
int grad[NMAX];

int cnt;
bool viz[NMAX];
void dfs(int nod)
{
    viz[nod] = 1;
    cnt++;
    for (int x : g[nod])
        if (!viz[x])
            dfs(x);
}

void euler(int nod)
{
    while (!g[nod].empty())
    {
        int x = *g[nod].begin();
        g[nod].erase(g[nod].begin());
        g[x].erase(g[x].find(nod));
        euler(x);
    }
    sol.push_back(nod);
}
int main()
{
    ifstream cin("ciclueuler.in");
    ofstream cout("ciclueuler.out");
    int n, m, i;
    cin >> n >> m;
    while (m--)
    {
        int a, b;
        cin >> a >> b;
        g[a].insert(b);
        g[b].insert(a);
        grad[a]++;
        grad[b]++;
    }
    dfs(1);
    bool ok = 0;
    for (i = 1; i <= n; i++)
        if (grad[i] % 2)
        {
            ok = 1;
            break;
        }
    if (cnt != n or ok)
    {
        cout << -1;
        return 0;
    }
    euler(1);
    for (i = sol.size() - 1; i > 0; i--)
        cout << sol[i] << ' ';
}