#include <iostream>
#include <fstream>
#include <cmath>
#include <vector>
#include <bitset>
#include <queue>
#include <deque>
#include <list>
#include <set>
#include <ctime>
#include <string>
#include <cstring>
#include <iomanip>
#include <algorithm>
using namespace std;
ifstream ff("ciclueuler.in");
ofstream gg("ciclueuler.out");
#define max 100001

int n, m, dd[max], qq[max];
vector<int> vv[max], rr;
vector<int>::iterator it;
bool ww[max];

void dfs(int x){
	int l=vv[x].size();
	ww[x]=1;
	for(int i=0;i<l;i++)
	if(!ww[vv[x][i]]) dfs(vv[x][i]);
}

void del(int x,int y){
	vv[x].pop_back();
	for(it=vv[y].begin();it!=vv[y].end();it++)
	if(*it==x){ vv[y].erase(it); return; }
}

void eul(){
	dfs(1);
	for(int i=1;i<=n;i++)
	if(!ww[i] || dd[i]%2){
		cout << "-1\n";
		return;
	}
	int p=0, x, l;
	qq[p++]=1;
	while(p>0){
		x=qq[p-1];
		l=vv[x].size();
		if(l==0){
			rr.push_back(x);
			p--;
			continue;
		}
		qq[p++]=vv[x][l-1];
		del(x,vv[x][l-1]);
	}
	for(it=rr.begin();it!=rr.end()-1;it++) gg << *it << " ";
}

int main(){
	int a, b;
	ff >> n >> m;
	for(int i=0;i<m;i++){
		ff >> a >> b;
		dd[a]++; dd[b]++;
		vv[a].push_back(b);
		vv[b].push_back(a);
	}
	eul();
}