#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define pi pair<int,int>
#define pl pair<long long,long long>
#define rd(x) cin >> x;
#define rda(a,n) for(int i=1;i<=n;i++) cin >> a[i];
#define wr(x) cout << x << ' ';
#define wrl(x) cout << x << '\n';
#define wra(a,n) for(int i=1;i<=n;i++) cout << a[i] << ' '; cout << '\n';
#define lg length()
#define pb push_back
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005

int n,m,x,y,v[100005],d[100005],s[100005];

vector <pair<int,bool>> g[100005];
vector <int> p;

list <int> ans;
list <int>::iterator t[100005],curr;

void Euler(int nod){
    if(!v[nod]){
        t[nod]=curr;
        t[nod]--;
        v[nod]=1;
    }
    for(int i=0;i<g[nod].size();i++){
        if(!g[nod][i].second){
            ans.insert(curr,g[nod][i].first);
            g[nod][i].second=1;
            if(nod==g[nod][i].first) continue;
            for(int j=0;j<g[g[nod][i].first].size();j++){
                if(!g[g[nod][i].first][j].second && g[g[nod][i].first][j].first==nod){
                    g[g[nod][i].first][j].second=1;
                    break;
                }
            }
            Euler(g[nod][i].first);
            return;
        }
    }
    d[nod]=1;
}

int32_t main(){
    ios_base :: sync_with_stdio(0);
    in >> n >> m;
    for(int i=1;i<=m;i++){
        in >> x >> y;
        g[x].pb({y,0});
        if(x!=y) g[y].pb({x,0});
        s[x]++; s[y]++;
    }
    for(int i=1;i<=n;i++){
        if(s[i]%2){
            out << -1;
            return 0;
        }
    }
    ans.insert(ans.end(),1);
    t[1]=ans.begin();
    v[1]=1;
    x=1;
    while(x<=n){
        if(d[x]) x++;
        else{
            curr=t[x]; curr++;
            Euler(x);
        }
    }
    for(int i : ans){
        p.pb(i);
    }
    for(int i=0;i<p.size()-1;i++) out << p[i] << ' ';
}