#include<fstream>
#include<vector>
#include<stack>
#define N 100100
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector< pair<int,int> >v[N];
pair<int,int> muchie;
stack<int> s;
int nod,n,m,i,x,y,gr[N],E[5*N],e;
bool used[5*N],viz[N];
void dfs(int x)
{
    viz[x]=1;
    for(int k=0;k<v[x].size();++k)
        if(!viz[v[x][k].first])
            dfs(v[x][k].first);
}
int main ()
{
    f>>n>>m;
    for(i=1;i<=m;++i)
    {
        f>>x>>y;
        v[x].push_back(make_pair(y,i));
        v[y].push_back(make_pair(x,i));
        gr[x]++;
        gr[y]++;
    }
    for(i=1;i<=n;++i)
        if(!gr[i])
            viz[i]=1;
    for(i=1;i<=n;++i)
        if(gr[i])
        {
            dfs(i);
            break;
        }
    s.push(i);
    for(i=1;i<=n;++i)
        if((gr[i]%2)||(!viz[i]))
        {
            g<<"-1";
            return 0;
        }
    while(!s.empty())
    {
        nod=s.top();
        if(v[nod].empty())
        {
            E[++e]=nod;
            s.pop();
        }
        else
        {
            muchie=v[nod][v[nod].size()-1];
            if(used[muchie.second])
                v[nod].pop_back();
            else
            {
        v[nod].pop_back();
                used[muchie.second]=1;
                s.push(muchie.first);
            }
        }
    }
    for(i=1;i<e;++i)
        g<<E[i]<<" ";
    return 0;
}