#include <bits/stdc++.h>
using namespace std;
#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<int>
#define VP vector<pair<int, int> >
#define FASTIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define index INDEX
#ifdef _WIN32
#include <windows.h>
#define print(x) PRINT(x, #x)
template<typename T> inline const void PRINT(T VARIABLE, string NAME)
{
#ifndef ONLINE_JUDGE /// ONLINE_JUDGE IS DEFINED ON CODEFORCES
    HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
    SetConsoleTextAttribute(hConsole, 10);
    cerr << NAME << " = " << VARIABLE;
    SetConsoleTextAttribute(hConsole, 7);
    cerr << '\n';
#endif
}
#else
#define print(x) 0
#endif
typedef long long ll;
typedef unsigned long long ull;
const ll INFLL = 2 * (ll)1e18 + 100;
const int INFINT = 2 * (int)1e9 + 100;
const double PI = atan(1) * 4;
const double EPS = 1e-9;
const int SEED = 1e3 + 7;

const int MOD = 1e9 + 7; /// careful here (7 or 9, 66.. etc)25000033
const int NMAX = 1e5 + 5;

int n, m;
multiset<int> graf[NMAX];
V parcurgere;
void euler(int nod)
{
    while(!graf[nod].empty())
    {
        int i = *(graf[nod].begin());
        graf[nod].erase(graf[nod].begin());
        graf[i].erase(graf[i].find(nod));
        euler(i);
    }
    parcurgere.pb(nod);
}

int main()
{


    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    FASTIO;
    cin >> n >> m;
    for1(i, m)
    {
        int a, b;
        cin >> a >> b;
        graf[a].insert(b);
        graf[b].insert(a);
    }
    for1(i, n) if(graf[i].size() % 2) return cout << -1, 0;
    euler(1);
    parcurgere.pop_back();
    for(auto i: parcurgere) cout << i << ' ';

    return 0;
}