#include <stdio.h>
#include <vector>
#define NMAX 100005
#define LMAX 500005
#define pb push_back
#define pii pair <int,int> 
#define mp make_pair
#define f first
#define s second
using namespace std;
int n,m,tip,r,sol[LMAX];
vector <pii> A[NMAX];
char viz[NMAX];
void read()
{
	scanf("%d%d",&n,&m);
	int i,x,y;
	for (i=1; i<=m; i++)
	{
		scanf("%d%d",&x,&y);
		A[x].pb(mp(y,i));
		A[y].pb(mp(x,i));
	}
	for (i=1; i<=n; i++)
		if (A[i].size() & 1)
		{
			tip=1;
			break ;
		}
}
void euler(int nod)
{
	int i;
	for (i=0; i<A[nod].size(); i++)
		if (!viz[A[nod][i].s])
		{
			viz[A[nod][i].s]=1;
			euler(A[nod][i].f);
		}
	sol[++r]=nod;
}
int main()
{
	freopen("ciclueuler.in","r",stdin);
	freopen("ciclueuler.out","w",stdout);
	read();
	if (tip)
	{
		printf("-1\n");
		return 0;
	}
	euler(1);
	if (r!=m+1)
	{
		printf("-1\n");
		return 0;
	}	
	for (int i=r; i>1; i--)
		printf("%d ",sol[i]);
	printf("\n");
	return 0;
}