#include <bits/stdc++.h>
#define nMax 100005
#define mMax 500005
using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector <int> v[nMax];
vector <int> sol;
int n, m;
int st[mMax], dr[mMax], poz[mMax];
bool viz[mMax];
inline void Citire()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i ++)
    {
        int x, y;
        fin >> x >> y;
        st[i] = x;
        dr[i] = y;
        v[x].push_back(i);
        v[y].push_back(i);
    }
}

inline bool euler()
{
    for(int i = 1; i <= n; i ++)
        if(v[i].size() % 2 == 1)
            return false;
    return true;
}

inline void dfs(int nod)
{
    int k;
    while(poz[nod] < v[nod].size())
    {
        k = v[nod][poz[nod] ++];
        if(!viz[k])
        {
            viz[k] = 1;
            dfs(st[k] + dr[k] - nod); 
        }
    }
    sol.push_back(nod);
}

inline void Solve()
{
    dfs(1);
    for(auto it : sol)
        fout << it << ' ';
}

int main()
{
    Citire();
    if(euler() == false)
        fout << -1;
    else
        Solve();
    return 0;
}