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