#include <cstdio>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <algorithm>
#include <utility>
#include <string>
#include <functional>
#include <sstream>
#include <fstream>
#include <iostream>
using namespace std;
#define FOR(i,a,b) for (i=a;i<=b;i++)
#define fori(it,v) for (it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define mp make_pair
#define fs first
#define ss second
#define all(c) c.begin(),c.end()
#define pf push_front
#define popb pop_back
#define popf pop_front
FILE *in,*out;
typedef pair<int,int> ii;
stack<ii> q;
vector<ii> a[100005];
vector<bool> viz(500005,false);
int nr[100005];
void afis()
{
	if (q.empty())
		return ;
	int x=q.top().fs;
	q.pop();
	afis();
	fprintf(out,"%d ",x);
}
int main()
{
	int n,m,x,y,i;
	in=fopen("ciclueuler.in","r");
	out=fopen("ciclueuler.out","w");
	fscanf(in,"%d%d",&n,&m);
	FOR(i,1,m)
	{
		fscanf(in,"%d%d",&x,&y);
		a[x].pb(mp(y,i));
		a[y].pb(mp(x,i));
		nr[x]++;
		nr[y]++;
	}
	FOR(i,1,n)
		if (nr[i]%2==1)
		{
			fprintf(out,"-1\n");
			fclose(in);
			fclose(out);
			return 0;
		}
	q.push(mp(1,-1));
	while (!q.empty())
	{
		ii nod=q.top();
		q.pop();
		nod.ss++;
		q.push(nod);
		if (nod.ss==nr[nod.fs])
		{
			q.pop();
			if (!q.empty())
				viz[a[q.top().fs][q.top().ss].ss]=0;
			continue;
		}
		if (viz[a[nod.fs][nod.ss].ss])
			continue ;	
		viz[a[nod.fs][nod.ss].ss]=1;
		q.push(mp(a[nod.fs][nod.ss].fs,-1));
		if (q.size()==m+1)
		{
			afis();
			fclose(in);
			fclose(out);
			return 0;
		}
	}
	fclose(in);
	fclose(out);
	return 0;
}