#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int nmax = 500005;

int n, m, st[nmax], dr[nmax], poz[nmax];
bool used[nmax];
vector < int > L[nmax], ans;

void read()
{
    fin >> n >> m;
    for(int i = 1; i <= m; ++i)
    {
        fin >> st[i] >> dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
}

bool euler()
{
    for(int i = 1; i <= n; ++i)
        if(L[i].size() & 1)
            return false;
    return true;
}

void dfs(int nod)
{
    int x;
    while(L[nod].size() > poz[nod])
    {
        x = L[nod][poz[nod]++];
        if(!used[x])
        {
            used[x] = true;
            dfs(st[x] + dr[x] - nod);

        }
    }
    ans.push_back(nod);
}

void solve()
{
    if(!euler())
        fout << "-1\n";
    else
    {
        dfs(1);
        ans.pop_back();
        for(auto it: ans)
            fout << it << " ";
        fout << "\n";
    }
}

int main()
{
    read();
    solve();
    return 0;
}