# include <stack>
# include <vector>
using namespace std;
int n,m,i,k,x,y,rez[100002],nr;
vector <int> G[600002];
vector <int>::iterator it;
stack <int> S;
int main()
{
	freopen("ciclueuler.in","r",stdin);
	freopen("ciclueuler.out","w",stdout);
	scanf("%d %d", &n, &m);
	for (i=1;i<=m;i++)
	{
		scanf("%d %d", &x, &y);
		G[x].push_back(y),G[y].push_back(x);
	}
	for (i=1;i<=n;i++)
		if (G[i].size()%2)
		{
			printf("-1");
			return 0;
		}
	S.push(1);
	while (!S.empty())
	{
		x=S.top();
		if (!G[x].size())
		{
			rez[++nr]=x,S.pop();
			continue;
		}
		y=G[x].back(),G[x].pop_back();
		S.push(y);
		for (it=G[y].begin();it!=G[y].end();++it)
			if (*it==x)
				{
					G[y].erase(it);
					break;
				}
	}
	for (i=nr;i>=1;i--) printf("%d ", rez[i]);
	return 0;
}