#include <bits/stdc++.h>
#define NMAX 100100

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
list< int > v[NMAX];
int n,m,conex;
int fr[NMAX],gr[NMAX];
bool ok=true;
vector<int>sol;
int p;
void euler(int i)
{

    while(!v[i].empty())
    {
        int val=v[i].front();
        v[i].pop_front();
        v[val].erase(find(v[val].begin(),v[val].end(),i));
        euler(val);
    }

    sol.push_back(i);
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int x,y;
        fin>>x>>y;
        ++gr[x];
        ++gr[y];

       v[x].push_back(y);
       v[y].push_back(x);


    }
    for(int i=1;i<=n&&ok;++i)
    {
        if(gr[i]%2==1){ok=false;continue;}

    }
    if(!ok)fout<<-1;
    else
    {
        euler(1);
       for(auto x:sol)fout<<x<<" ";
    }
    return 0;
}