#include <cstdio>
#include <vector>
#include <utility>
#include <list>
#include <stack>
using namespace std;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
FILE *in,*out;
list<int> a[100005];
int sters [500005];
int gr[100005];
vector<int> rez;
stack<int> s;
/*void euler(int x)
{
	int i;
	for (i=0;i<a[x].size();i++)
		if (!sters[a[x][i].se])
		{
			sters[a[x][i].se]=1;
			euler(a[x][i].fi);
		}
	rez.pb(x);
}*/
int main()
{
	int n,m,x,y,i,nod,aux,next;
	list<int>::iterator it;
	in=fopen("ciclueuler.in","r");
	out=fopen("ciclueuler.out","w");
	fscanf(in,"%d%d",&n,&m);
	for (i=1;i<=m;i++)
	{
		fscanf(in,"%d%d",&x,&y);
		gr[x]++;
		gr[y]++;
		a[x].pb(y);
		a[y].pb(x);
	}
	for (i=1;i<=n;i++)
		if (gr[i]%2==1)
		{
			fprintf(out,"-1\n");
			fclose(in);
			fclose(out);
			return 0;
		}
	s.push(1);
	while (!s.empty())
	{
		nod=s.top();
		s.pop();
		while (1)
		{
			if (a[nod].empty())
			{
				rez.pb(nod);
				break;
			}
			next=a[nod].front();
			a[nod].pop_front();
			for (it=a[next].begin();it!=a[next].end();++it)
				if (*it==nod)
				{
					a[next].erase(it);
					break;
				}
			s.push(nod);
			nod=next;
		}
	}
	if (rez.size()!=m+1)
		fprintf(out,"-1\n");
	else
	{
		for(i=rez.size()-1;i>0;i--)
			fprintf(out,"%d ",rez[i]);
		fprintf(out,"\n");
	}
	fclose(in);
	fclose(out);
	return 0;
}