#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <ctime>
#include <cassert>
using namespace std;

#define PRO "ciclueuler"
void OpenFiles(int EVAL)
{
	if(EVAL)
	{
		char input[100] = PRO, output[100] = PRO;
		freopen(strcat(input, ".in"),"r",stdin);
		freopen(strcat(output,".out"),"w",stdout);
	} else
	{
		freopen("test.in","r",stdin);
		freopen("test.out","w",stdout);
	}
}

#define MAX 100001
#define MOD 666013
#define INF 0xffffff
#define EPS 1E-8

int n, m, grad[MAX], m_viz[5*MAX];
vector<pair<int,int> >graf[MAX];
vector<int>ciclu;
stack<int>st;

void euler(int x)
{
	for(int i=1;i<=n;i++)
	if(grad[i]%2)
	{
		printf("-1");
		return;
	}
	st.push(x);
	while(st.size() > 0)
	{
		go_in:
		x = st.top();
		for(int i=0;i<graf[x].size();i++)
		if(!m_viz[ graf[x][i].second ])
		{
			m_viz[ graf[x][i].second ] = 1;
			st.push( graf[x][i].first );
			goto go_in;
		}
		ciclu.push_back(st.top());
		st.pop();
	}
	for(int i=ciclu.size()-1;i>0;i--)printf("%d ",ciclu[i]);
}

int main(int argv,char *args[])
{	
OpenFiles(argv==0);
	/* start code */
	scanf("%d %d",&n,&m);
	for(int i=1,x,y;i<=m;i++)
	{
		scanf("%d %d",&x,&y);
		graf[x].push_back(make_pair(y,i));
		graf[y].push_back(make_pair(x,i));
		grad[x]++;
		grad[y]++;
	}
	euler(1);
	/* end */
	return 0;
}