#include <cstdio>
#include <vector>
using namespace std;
#define DIM 100005
#define pb push_back
FILE *fout = fopen("ciclueuler.out", "w");
vector <int> A[DIM];
int n, m, d[DIM], v[DIM], grad[DIM];

void afis()
{
	for (int i =1 ; i <= n; ++i)
	{
		printf ("%d: ", i);
		for (int j =1 ; j <= d[i]; ++j)
			printf ("%d ", A[i][j]);
		printf ("\n");
	}
	printf ("||--------_||\n");
}

void stergeMuchie(int i, int k)
{
	
	for (int j = 1; j <= d[i] ;++j)
		if (A[i][j] == k)
		{
			A[i][j] *= -1;
			--A[i][0];
			return;
		}
	
}

void euler(int i)
{
	int j = 0;
	while (A[i][0])
	{
		++j;
		if (A[i][j] > 0)
		{
			stergeMuchie(i, A[i][j]);
			if (i != -A[i][j])
				stergeMuchie(-A[i][j], i);
	//		afis();
			euler(-A[i][j]);
		}
	}
	
	fprintf (fout, "%d ", i);
}

void DFS(int i)
{
	v[i] = 1;
	for (int j = 1; j <= A[i][0]; ++j)
		if (!v[A[i][j]])
			DFS(A[i][j]);
}

bool conex()
{
	
	DFS(1);
	
	for (int i = 1; i <= n; ++i)
		if (!v[i])
			return false;
	
	return true;
}

bool toate_pare()
{
	for (int i = 1; i <= n; ++i)
		if (grad[i] % 2 != 0)
		{
			
			return false;
		}
	
	return true;
}

int main()
{
	FILE *f = fopen("ciclueuler.in", "r");
	fscanf(f, "%d%d", &n, &m);
	for (int i = 1; i <= n; ++i)
		A[i].pb(0);
	
	for (int i = 1, x, y; i <= m; ++i)
	{
		fscanf(f, "%d%d", &x, &y);
		++A[x][0];++d[x];
		A[x].pb(y);
		++grad[x], ++grad[y];
		if (x != y)
			++A[y][0], A[y].pb(x), ++d[y];
	}
//	afis();
	if (!conex() || !toate_pare())
		fprintf(fout, "-1\n");
	else
		euler(1);
	fclose(f);
	fclose(fout);
	return 0;
}