#include <bits/stdc++.h>
using namespace std;
ifstream f("ciclueuler.in"); ofstream g("ciclueuler.out");
int n,m,gr[100005],vizm[500005],vizn[100005];
vector <pair <int, int> > L[100005];
stack <int> S;
vector <int> C;
void dfs(int nod)
{   vizn[nod]=true;
    for(unsigned int i=0;i<L[nod].size();++i)
        if(!vizn[L[nod][i].first]) dfs(L[nod][i].first);
}
int main()
{   f>>n>>m;
    for(int a,b,i=1;i<=m;++i)
    {   f>>a>>b;
        L[a].push_back(make_pair(b,i)); gr[a]++;
        L[b].push_back(make_pair(a,i)); gr[b]++;
    }
    dfs(1);
    for(int i=1;i<=n;++i)
        if(!vizn[i]) {g<<-1; g.close(); f.close();return 0;}
    for(int i=1;i<=n;++i)
        if(gr[i]%2) {g<<-1; g.close(); f.close(); return 0;}
    S.push(1);
    while(!S.empty())
    {   int nod=S.top();
        if(!gr[nod]) {C.push_back(nod); S.pop();}
        else
        {   /// din capat, scot tot ce a fost vizitat deja pentru a ajugne la un nod bun
            while(vizm[L[nod].back().second]) L[nod].pop_back();
            int nod1=L[nod].back().first; ///nod bun
            gr[nod]--;
            gr[nod1]--;
            vizm[L[nod].back().second]=true;
            L[nod].pop_back();
            S.push(nod1);
        }
    }
    for(int i=C.size()-1;i;--i) g<<C[i]<<" ";
    g.close(); f.close(); return 0;
}