#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector <int> G[100005];
stack <int> st;
int viz[100005];
void eulerian(int node)
{
	int other;
	while(!G[node].empty())
	{
		st.push(node);
		other=G[node].back();
		G[node].pop_back();
		G[other].erase(find(G[other].begin(),G[other].end(),node));
		node=other;
	}
}
void dfs(int u)
{
	int v,j;
	viz[u]=1;
	for(j=0;j<G[u].size();j++)
		{
			v=G[u][j];
			if(viz[v]==0)
			   dfs(v);
		}
}
int main()
{
	int n,m,i,j,x,y,node;
	bool conex=1,nrpare=1;
	fin>>n>>m;
	for(i=1;i<=m;i++)
		{
			fin>>x>>y;
			G[x].push_back(y);
			G[y].push_back(x);
		}
	dfs(1);
	for(i=1;i<=n;i++)
		{
		if(viz[i]==0)
			{
				conex=0;
				break;
			}
		if(G[i].size()%2==1)
		   {
		   nrpare=0;
		   break;
			}
		}
	if(nrpare==0 ||conex==0)
		{
			fout<<"-1\n";
			return 0;
		}
	node=1;
	do
	{
		eulerian(node);
		node=st.top();
		fout<<node<<" ";
		st.pop();
	}while(!st.empty());
    return 0;
}