#include <iostream>
#include <cstdio>
#include <list>
#include <stack>

#define Nmax 100005

using namespace std;

int n, m;
int viz[Nmax];
int grad[Nmax];
list <int> G[Nmax], sol;
stack <int> S;

void citire()
{
    scanf("%d %d",&n, &m);
    for (int i=1; i<=m; i++)
    {
        int x,y;
        scanf("%d %d",&x,&y);
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
}

void dfs(int nod)
{
    viz[nod] = 1;
    for (list<int> :: iterator it = G[nod].begin(); it != G[nod].end(); it++)
        if (!viz[*it])
            dfs(*it);
}

int conex()
{
    dfs(1);
    for (int i=1; i<=n; i++)
        if (!viz[i])
            return 0;
    return 1;
}

int gradePare()
{
    for (int i=1; i<=n; i++)
        if (grad[i] % 2 == 1)
            return 0;
    return 1;
}

void ciclu(int x)
{
    while(!G[x].empty())
    {
        int y = G[x].front();
        S.push(x);
        G[x].pop_front();
        for (list<int> :: iterator it=G[y].begin(); it != G[y].end(); it++)
            if (*it == x)
            {
                G[y].erase(it);
                break;
            }
        x = y;

    }
}

void afisare()
{
    for (list<int> :: iterator it = sol.begin(); it != sol.end(); it++)
        printf("%d ",*it);
}

void rezolvare()
{
    if (!(conex() && gradePare()))
        printf("-1");
    else
    {
        int x = 1;
        do
        {
            ciclu(x);
            x = S.top();
            S.pop();
            sol.push_back(x);

        }while(!S.empty());
        afisare();
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
    rezolvare();
    return 0;
}