#include <cstdio>
#include <vector>
using namespace std;
int n,m,cnt=0;
vector <pair<int,int> > v[100100];
vector <int> ciclu;
int grad[100100],c[500100],gr[100100];

int main()
{
	freopen ("ciclueuler.in","r",stdin);
	freopen ("ciclueuler.out","w",stdout);
	
	scanf("%d%d",&n,&m);
	int x,y;
	for (int i=1;i<=m;++i)
	{
		scanf("%d%d",&x,&y);
		if (x!=y)
		{
			v[x].push_back(make_pair(y,v[y].size()));
			v[y].push_back(make_pair(x,v[x].size()-1));
			++grad[x];
			++grad[y];
			++gr[x];
			++gr[y];
		}
		else
		{
			v[x].push_back(make_pair(x,v[x].size()));
			++grad[x];
			gr[x]+=2;
		}
	}
	
	bool k=0;
	for (int i=1;i<=n;++i)
		if (gr[i]&1)
			k=1;
	if (k)
	{
		printf("%d",-1);
		return 0;
	}
	int i=1;
	while (!grad[i])
		++i;
	int poz=1;
	c[1]=i;
	while (poz)
	{
		int nod=c[poz];
		if (!grad[nod])
		{
			ciclu.push_back(nod);
			c[poz--]=0;
			continue;
		}
		for (int j=0;j<v[nod].size();++j)
			if (v[nod][j].first)
			{
				--grad[nod];
				int aux=v[nod][j].first;
				if (aux!=nod)
					--grad[aux];
				v[nod][j].first=0;
				v[aux][v[nod][j].second].first=0;
				c[++poz]=aux;
				break;
			}
	}
	if (ciclu.size()!=m+1)
	{
		printf("%d\n",-1);
		return 0;
	}
	for (i=0;i<ciclu.size()-1;++i)
		printf("%d ",ciclu[i]);
	printf("\n");
	return 0;
}