#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>
#define Max_Size 100010
using namespace std;
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");
int N, M;
vector < int > V[Max_Size];
stack < int > Stack, Sol;

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

    for (int i = 1; i <= N; i++)
    {
        if (V[i].size() % 2)
        {
            fout << "-1\n";
            fout.close();
            return 0;
        }
    }

    Stack.push(1);

    while (!Stack.empty())
    {
        int nod = Stack.top();
        if (!V[nod].empty())
        {
            int vecin = V[nod][0];
            Stack.push(vecin);
            V[nod].erase(V[nod].begin());
            V[vecin].erase( find(V[vecin].begin(), V[vecin].end(), nod) );
        }
        else
        {
            Stack.pop();
            Sol.push(nod);
        }
    }

    if (Sol.size() - 1 != M)
    {
        fout << "-1\n";
        fout.close();
        return 0;
    }
    else
    {
        while (Sol.size() > 1)
        {
            fout << Sol.top() << ' ';
            Sol.pop();
        }
        fout << '\n';
        fout.close();
    }
    return 0;
}