# include <cstdio>
# include <stack>
# include <vector>
using namespace std;

FILE *f = freopen("ciclueuler.in", "r", stdin);
FILE *g = freopen("ciclueuler.out", "w", stdout);

const int N_MAX = 100001;
const int M_MAX = 500001;

struct Muchie{
    int index;
    int capat;

    Muchie (int& a, int& b)
    {
        this -> index = a;
        this -> capat = b;
    }
};

stack <int> stiva;
vector <Muchie> G[N_MAX];
vector <int> solutie;
int grad[N_MAX];
int vizitatM[M_MAX];
int n, m, M;
bool se_Poate;

void adauga(int& x, int& y)
{
    grad[x] ++;
    grad[y] ++;

    M++;

    G[x].push_back(Muchie(M, y));
    G[y].push_back(Muchie(M, x));
}

void read()
{
    scanf("%d %d", &n, &m);

    for (int i=1; i<=m; i++)
    {
        int x, y;
        scanf("%d %d", &x, &y);

        adauga(x, y);
    }
}

int sterge_vecin(int& nod)
{
    while (!G[nod].empty() && vizitatM[G[nod].back().index])
        G[nod].pop_back();

    if (!G[nod].empty())
    {
        int v = G[nod].back().capat;

        vizitatM[G[nod].back().index] = true;

        grad[nod] --;
        grad[v] --;

        M--;

        G[nod].pop_back();

        return v;
    }
    else return 0;
}

void solve()
{
    se_Poate = true;

    for (int i=1; i<=n; i++)
        if (grad[i] % 2 == 1)
            se_Poate = false;

    if (se_Poate)
    {
        int i;
        for (i=1; grad[i] == 0 && i<=n; i++);

        stiva.push(i);
        while (!stiva.empty())
        {
            int nod = stiva.top();

            if (grad[nod])
            {
                stiva.push(sterge_vecin(nod));
            }
            else
            {
                solutie.push_back(stiva.top());
                stiva.pop();
            }
        }
    }

    if (M > 0) se_Poate = false;
}

void write()
{
    if (se_Poate)
    {
        for (int i=0; i<solutie.size()-1; i++)
            printf("%d ", solutie[i]);

        printf("\n");
    }
    else printf("-1\n");
}

int main()
{
    read();
    solve();
    write();
    return 0;
}