#include <cstdio>
#include <vector>

using namespace std;

#define file_in "ciclueuler.in"
#define file_out "ciclueuler.out"

#define Nmax 101001

int n,m;
int viz[Nmax],grad[Nmax];
vector<int> G[Nmax];
vector<int> v[Nmax];

void dfs(int nod)
{
	
	for (int i=0;i<v[nod].size();++i)
		if (!viz[v[nod][i]])
		{
			 //printf("%d ", G[nod][i]);
			 viz[v[nod][i]]=1;
			 dfs(G[nod][i]);
		}
	printf("%d ", nod);	
}
	

int main()
{
	int i,a,b;
	freopen(file_in,"r",stdin);
	freopen(file_out,"w",stdout);
	
	scanf("%d %d", &n, &m);
	for (i=1;i<=m;++i)
	{
		scanf("%d %d", &a,&b);
		
		grad[a]++;
		grad[b]++;

		G[a].push_back(b);
		G[b].push_back(a);
		v[a].push_back(i);
		v[b].push_back(i);
	}
	
	for (i=1;i<=n;++i)
		 if (grad[i]%2==1)//grad impar
		 {
			 printf("-1\n");
			 return 0;
		 }
		 
	//memset(viz,0,sizeof(viz));	 
		 
	/*for (i=1;i<=n;++i)
		 if (!viz[i])*/
	dfs(1);
		 
	fclose(stdin);
	fclose(stdout);
	
	return 0;
	
}