#include<fstream>
#include<vector>
using namespace std;
ifstream f("fleury.in");
ofstream g("fleury.out");
const int Nmax=100100,Mmax=500500;
int n,m,x[Mmax],y[Mmax],sol[Mmax],nr;
bool viz[Mmax];
vector <int> G[Nmax];
inline void citire(){
	f>>n>>m;
	for(int i=1;i<=m;++i){
	{f>>x[i]>>y[i];
	G[x[i]].push_back(i);
	G[y[i]].push_back(i);
	}
	}
inline bool Eulerian(){
	for(int i=1;i<=n;++i)
		if(G[i].size()%2) return false;
	return true;
}
inline void Euler(int nod){
	vector<int>::iterator it=G[nod].begin(), sf=G[nod];
	for(;it!=sf;++it)
		if(!viz[*it]){
			viz[*it]=true;
			Euler(x[*it]+y[*it]-nod);
		}
	sol[++nr]=nod;
}
int main(){
	citire();
	if(Eulerian()){
		Euler(1);
		for(int i=1;i<=nr;++i) g<<sol[i]<<' ';
		g<<'\n';
	}
else g<<"-1\n";
return 0;
}