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

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
list< int > v[NMAX];
int gr[NMAX];
int n,m,conex;
bool ok=true;
vector<int>sol;
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){fout<<-1;return 0;}

    }

        euler(1);
        for(int i=sol.size()-1;i>=0;i--)
        fout<<sol[i]<<' ';

    return 0;
}