#include <stdio.h>
#include <vector>
#include <stack>
#define pii pair <int,int>
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define NMAX 100005
#define LMAX 500005
using namespace std;
int n,m,B[NMAX],x;
vector <pii> A[NMAX];
vector <int> sol;
bool viz[LMAX];
stack <int> st;
int main()
{
	freopen("ciclueuler.in","r",stdin);
	freopen("ciclueuler.out","w",stdout);
	scanf("%d%d",&n,&m);
	int i,a,b; 
	for (i=1; i<=m; i++)
	{
		scanf("%d%d",&a,&b);
		A[a].pb(mp(b,i));
		A[b].pb(mp(a,i));
		x=a;
	}
	for (i=1; i<=n; i++)
		if (A[i].size() & 1)
		{
			printf("-1\n");
			return 0;
		}
	st.push(x);
	int nod,edge,vec,find;
	while (!st.empty())
	{
		nod=st.top(); find=0;
		for (i=B[nod]; i<A[nod].size(); i++)
		{
			vec=A[nod][i].f; edge=A[nod][i].s;
			if (!viz[edge])
			{
				st.push(vec);
				viz[edge]=1;
				find=1;
				B[nod]++;
				break ;
			}
		}
		if (!find)
			sol.pb(nod),st.pop();
	}
	if (sol.size()!=m+1)
	{
		printf("-1\n");
		return 0;
	}
	for (i=sol.size()-1; i>0; i--)
		printf("%d ",sol[i]);
	printf("\n");
	return 0;
}