#include <algorithm>
#include <fstream>
#include <vector>
using namespace std;
int c[100002],ce[500002],viz[100002],p = 1, u = 1, nr;
vector<int> a[100002];
void ciclu(int x)
{
	nr = 1;
	c[1] = x;
	
	bool ok = true;
	
	do
	{
		for (int i = 0; (size_t) i < a[x].size() && ok; i++)
		{   int z = a[x][i];
			if (a[x][i] !=c[1])
			{
				nr++;
				c[nr] = a[x][i];
				x = z;
				break;
			}
			else 
			{	ok = false;
				c[++nr] = c[1];
			}
			
				vector<int>::iterator j = find(a[z].begin(), a[z].end(), x);
				a[z].erase(j);		
				a[x].erase(a[x].begin());
		}
	} while (ok);
}

void inser()
{
	for (int i = u; i >= p + 1; i--)
		ce[i + nr -1] = ce[i];
	
	for (int i = 2; i <= nr; i++)
		ce[p + i - 1] = c[i];
}

int main()
{
	ifstream in("ciclueuler.in");
	ofstream out("ciclueuler.out");
	
	int N, M;
	in >> N >> M;

	for (int i = 1; i <= M; i++)
	{	int x, y;
		in >> x >> y;		
		a[x].push_back(y);
		a[y].push_back(x);
	}

	for (int i = 1; i <= N; i++)
		if (a[i].size() % 2 !=0 || (viz[i] == 0 && a[i].size() != 0))
		{	out << -1;
			return 0;
		}
	
	ce[1] = 1;
	
	while (p <= u)
	{
		if (a[ce[p]].size())
		{
			ciclu(ce[p]);
			inser();
			
			u += nr - 1;
		}
		else
			p++;
	}
	
	for (int i = 1; i <= u-1; i++)
		out << ce[i] << ' ';
}