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

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

struct muchie
{
    int x, y;
    bool viz;

    int opposite(int a)
    {
        if(a == x)
            return y;
        return x;
    }
} muchii[500005];

vector<int> graf[100005];
int nrViz[100005];
bool viz[100005];
int n, m;
stack<int> S;

void citire()
{
    f>>n>>m;
    for(int i = 0; i<m; i++)
    {
        f>>muchii[i].x>>muchii[i].y;
        graf[muchii[i].x].push_back(i);
        graf[muchii[i].y].push_back(i);
    }
}

void dfs(int currNode)
{
    viz[currNode] = true;
    for(int i : graf[currNode])
    {
        int nod = muchii[i].opposite(currNode);
        if(!viz[nod])
        {
            dfs(nod);
        }
    }
}

bool verif()
{
    for(int i=1; i<=n; i++)
    {
        if(graf[i].size()%2 != 0 || (viz[i] == 0 && graf[i].size() != 0))
            return false;
    }
    return true;
}

void parcInit()
{
    S.push(1);
    while(!S.empty())
    {
        int currNod = S.top();
        if(!graf[currNod].empty())
        {
            int mch = graf[currNod].back();
            graf[currNod].pop_back();
            if(!muchii[mch].viz)
            {
                S.push(muchii[mch].opposite(currNod));
                muchii[mch].viz = true;
            }
        }
        else
        {
            if(S.size() > 1)
                g<<currNod<<" ";
            S.pop();
        }
    }
}

int main()
{
    citire();
    dfs(1);
    if(!verif())
    {
        g<<"-1";
    }
    else
        parcInit();
    return 0;
}