#include <fstream>
#include <vector>
#include <list>
#include <stack>
#define N_Max 100010
#define M_Max 500010
using namespace std;
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");
int N, M, grad_impar, neconex, Sol[M_Max];
list < int > L[N_Max];
stack < int > S;

void Delete_From_List(int i, int nod)
{
    for (list < int > :: iterator it = L[i].begin(); it != L[i].end(); it++) {
        if (*it == nod) {
            L[i].erase(it);
            return;
        }
    }
}

int main()
{
    fin >> N >> M;
    for (int x, y, i = 1; i <= M; i++) {
        fin >> x >> y;
        L[x].push_back(y);
        L[y].push_back(x);
    }

    for (int i = 1; i <= N; i++) {
        if (L[i].size() & 1) {
            grad_impar = 1;
            break;
        }
    }

    S.push(1);

    while (!S.empty())
    {
        int nod = S.top();
        if (L[nod].size())
        {
            S.push(L[nod].front());
            Delete_From_List(L[nod].front(), nod);
            L[nod].erase(L[nod].begin());
        }
        else
        {
            Sol[++Sol[0]] = nod;
            S.pop();
        }
    }

    if (Sol[0] - 1 != M) neconex = 1;

    if (grad_impar || neconex) {
        fout << "-1\n";
    }
    else
    {
        for (int i = Sol[0]; i >= 2; i--) {
            fout << Sol[i] << ' ';
        }
        fout << '\n';
    }

    fout.close();
    return 0;
}