#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
#define pb push_back
#define fi first
#define se second

ifstream fin("euler.in");
ofstream fout("euler.out");

const int M = 5e5+3;

int n;
bitset<M> u;
stack<int> stk;
vector<pii> e;
vector<int> r;
vector<vector<int>> adj;

void read(), euler();

int main()
{
    read();
    
    for (int i = 1; i <= n; i++)
        if (adj[i].size() % 2){ fout << -1; return 0; }
    
    euler();
    r.pop_back();
    for (auto it: r) fout << it << ' ';

    return 0;
}

void read(){
    int m; fin >> n >> m;
    adj.resize(n+1);
    for (int i = 0; i < m; i++){
        int a, b; fin >> a >> b;
        adj[a].pb(i); adj[b].pb(i);
        e.pb({a,b});
    }
}
void euler(){
    stk.push(1);
    while (!stk.empty()){
        int nod = stk.top(); 
        if (adj[nod].size()) {
            int m = adj[nod].back(); adj[nod].pop_back();
            if (u[m]) continue; u[m] = 1;
            stk.push(nod == e[m].fi ? e[m].se : e[m].fi);
        }
        else { stk.pop(); r.pb(nod); }
    }
}