#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fi("ciclueuler.in");
ofstream fo("ciclueuler.out");
const int NMAX=1e5+5;
int n,m,x,y,VIZ[NMAX*5],edge,nod,ok;
vector <pair<int,int>> V[NMAX];
vector <int> sol;
stack <int> curr;
int main()
{
	fi>>n>>m;
	for(int i=1;i<=m;i++)
	{
		fi>>x>>y;
		V[x].push_back({y,i});
		V[y].push_back({x,i});
	}
	for(int i=1;i<=n;i++)
		if(V[i].size()%2)
		{
			fo<<"-1\n";
			return 0;
		}
	edge=m;
	curr.push(1);
	while(!curr.empty())
	{
		nod=curr.top();
		while(!V[nod].empty() && VIZ[V[nod].back().second])
            V[nod].pop_back();
        if(!V[nod].empty())
        {
            y=V[nod].back().first;
            VIZ[V[nod].back().second]=1;
            V[nod].pop_back();
            edge--;
            curr.push(y);
        }
		else
		{
			sol.push_back(nod);
			curr.pop();
		}
	}
	sol.pop_back();
	for(auto x:sol)
		fo<<x<<" ";
	fi.close();
	fo.close();
	return 0;
}