#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <stack>
#include <queue>
#include <list>
//#include <windows.h>
//#include <conio.h>
#include <cstdlib>
#include <time.h>
#include <limits.h>
#include <string>
#include <math.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
#define ull unsigned ll
#define MOD 1000000007
#define INF (1<<31)-1
#define MINF -(1<<31)
#define vi vector <int>
#define vll vector <ll>
#define pii pair <int,int>
#define pll pair <ll,ll>
#define newl printf("\n")
int N,M,dg[100005];
bool used[100005];
list <int> G[100005],L;
queue <int> Q;
stack <int> S;
void BFS(int nod)
{
    Q.push(nod); used[nod]=true;
    while (!Q.empty())
    {
        nod=Q.front(); Q.pop();
        for (list<int>::iterator it=G[nod].begin();it!=G[nod].end();it++)
            if (!used[*it]) Q.push(*it),used[*it]=true;
    }
}
bool isConnected()
{
    BFS(1);
    for (int i=2;i<=N;i++)
        if (!used[i]) return false;
    return true;
}
bool eulerian()
{
    if (!isConnected()) return false;
    for (int i=1;i<=N;i++)
        if (dg[i]&1) return false;
    return true;
}
void del(int x,int y)
{
    dg[x]--,dg[y]--; G[x].pop_front();
    for (list<int>::iterator it=G[y].begin();it!=G[y].end();it++)
    {
        if (*it==x)
        {
            G[y].erase(it);
            break;
        }
    }
}
void euler(int nod)
{
    while (true)
    {
        if (G[nod].empty()) break;
        int x=G[nod].front();
        S.push(nod);
        del(nod,x);
        nod=x;
    }
}
int solve()
{
    int nod=eulerian();
    if (nod==0) return -1;
    do
    {
        euler(nod);
        nod=S.top(); S.pop();
        L.pb(nod);
    } while (!S.empty());
    return 1;
}
void write(int x)
{
    if (x==-1) printf("-1");
    else for (list<int>::iterator it=L.begin();it!=L.end();it++) printf("%d ",*it);
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d",&N,&M);
    while (M--)
    {
        int x,y;
        scanf("%d %d",&x,&y);
        G[x].pb(y); dg[x]++;
        G[y].pb(x); dg[y]++;
    }
    write(solve());
    return 0;
}