#include <bits/stdc++.h>
#define for0(i,n) for(int i=0; i<n; i++)
#define for1(i,n) for(int i=1; i<=n; i++)
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define V vector<short>
#define VP vector<pair<short, short> >
#define clr(A,x) memset(A, x, sizeof(A))
#define cpy(A,B) memcpy(A, B, sizeof(B))
#define g(s) getline(cin, s) ///ai grija la fin/cin ///
#define FASTIO ios_base::sync_with_stdio(0)
const long long INFLL = (1LL<<62);
const int INFINT = 2000000000;
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
/*template <typename T>
string to_string(const T& n){
    ostringstream os;
    os << n;
    return os.str();
}
*/
/*void invers_modular(int a, int b, int &d, int &x, int &y)
{
    if(!b)
    {
        d=a;
        x=1;
        y=0;
        return ;
    }
    int x0, y0;
    invers_modular(b, a%b, d, x0, y0);
    x=y0;
    y=x0-a/b*y0;
}*/ // daca x<0 se aduna cu mod pana e mai mare, x fiind rezultatul

/*ull putere(ull baza, ull exponent, ull MOD)
{
    if(exponent == 0) return 1;
    if(exponent % 2 == 0) return putere((baza * baza) % MOD, exponent / 2, MOD) % MOD;
    return ((baza % MOD) * (putere(baza, exponent - 1, MOD) % MOD) % MOD);
}*/
ifstream fin("ciclueuler.in"); /// modifica cu numele corespunzator
ofstream fout("ciclueuler.out"); /// modifica cu numele corespunzator

const int NMAX = 100005;
const int MMAX = 500005;

int n, m;
V graf[NMAX], EULER;
int noduri_prin_care_am_trecut[MMAX], contor;

void sterge(int y, int x)
{
    for0(i, graf[y].size())
        if(graf[y][i] == x)
        {
            swap(graf[y][i], graf[y][graf[y].size() - 1]);
            graf[y].pop_back();
            break;
        }
}

void euler()
{
    while(contor > 0)
    {
        if(graf[noduri_prin_care_am_trecut[contor]].size() > 0)
        {
            int aux = graf[noduri_prin_care_am_trecut[contor]][0];
            sterge(aux, noduri_prin_care_am_trecut[contor]);
            sterge(noduri_prin_care_am_trecut[contor], aux);
            noduri_prin_care_am_trecut[++contor] = aux;
        }
        else
        {
            contor--;
            if(contor > 0)
                EULER.pb(noduri_prin_care_am_trecut[contor]);
        }
    }
}


int main()
{
    fin >> n >> m;
    for1(i, m)
    {
        int x, y;
        fin >> x >> y;
        graf[x].pb(y);
        graf[y].pb(x);
    }
    for1(i, n)
        if(graf[i].size() % 2)
            return fout << -1, 0;

    contor = 1;
    noduri_prin_care_am_trecut[1] = 1;
    euler();
    for(auto i: EULER)
        fout << i << ' ';


    return 0;
}