#include<stdio.h>
#include<vector>
#define N 500001

using namespace std;
vector <int> a[N];
vector <pair <int,int> > muchii;
vector <bool> marcat;
int nr, n,m,c[N];
inline int nod(int nrm, int x)
{
	if (muchii [nrm].first == x)
		return muchii [nrm].second;
	return muchii [nrm].first;
}	

void citire()
{
	int x,y;
	scanf("%d%d",&n,&m);
	for(int i=0;i<m;i++)
		{
			scanf("%d%d",&x,&y);
			muchii.push_back ( make_pair (x,y) );
			marcat.push_back (false);
			a[x].push_back (i);
			a[y].push_back (i);
	}
}

void euler(int x)
{
	int i,y,nrm;
	for(i=0;i<a[x].size();i++)
	{
		nrm=a[x][i];
		if(marcat[nrm])
			continue;
		marcat [nrm] = true;
		y= nod(nrm,x);
		euler(y);
	}
	
	c[++nr] =x;
}
int main()

{
	freopen("ciclueuler.in","r",stdin);
	freopen("ciclueuler.out","w",stdout);
	citire();
	for (int i=1;i<=n;i++)
		if (a[i].size()%2)
		{
			printf("-1\n");
			return 0;
		}
	euler(1);
	if(nr!=m+1 || c[1]!=1)
	{
		printf("-1\n");
		return 0;
	}
	for (int i=nr;i>1;i--)
		printf("%d ",c[i]); 
    

	return 0;
}