#include <fstream>
#include <vector>
#include <bitset>
#include <stack>

using namespace std;

const int N = 1e5;
const int M = 5e5;

struct muchie
{
    int x, y;
};

muchie e[M];
bitset <M> sterse;
int n, m, prim[N+1];

vector <int> a[N+1];
vector <int> ce;

bool toate_gradele_pare()
{
    for (int i = 1; i <= n; i++)
    {
        if (a[i].size() % 2 != 0)
        {
            return false;
        }
    }
    return true;
}

int celalalt_vf(muchie e, int x)
{
    return (e.x + e.y - x);
}

int prima_muchie_nestearsa(int x)
{
    int i = prim[x];
    while (i < (int)a[x].size())
    {
        if (!sterse[a[x][i]])
        {
            return i;
        }
        i++;
    }
    return i;
}

void euler(int x)
{
    stack <int> stiva;
    stiva.push(x);
    while (!stiva.empty())
    {
        int x = stiva.top();
        prim[x] = prima_muchie_nestearsa(x);
        if (prim[x] < (int)a[x].size())
        {
            int i_e_c = a[x][prim[x]++];
            muchie e_c = e[i_e_c];
            int y = celalalt_vf(e_c, x);
            sterse[i_e_c] = 1;
            stiva.push(y);
        }
        else
        {
            stiva.pop();
            ce.push_back(x);
        }
    }
}

int main()
{
    ifstream in("ciclueuler.in");
    ofstream out("ciclueuler.out");
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        in >> e[i].x >> e[i].y;
        a[e[i].x].push_back(i);
        a[e[i].y].push_back(i);
    }
    in.close();
    if (!toate_gradele_pare())
    {
        out << "-1";
        out.close();
        return 0;
    }
    euler(1);
    if ((int)ce.size() != m + 1)
    {
        out << "-1";
        out.close();
        return 0;
    }
    for (int i = 0; i < (int)ce.size() - 1; i++)
    {
        out << ce[i] << " ";
    }
    out.close();
    return 0;
}