#include <bits/stdc++.h>
//#pragma GCC optimize ("03")
#define FastIO ios_base::sync_with_stdio(false) , cin.tie(0) , cout.tie(0)
#define FILES freopen("ciclueuler.in" , "r" , stdin) , freopen("ciclueuler.out" , "w" , stdout)
#define ll long long
#define ull unsigned long long
#define ld long double
#define eb emplace_back
#define pb push_back
#define qwerty1 first
#define qwerty2 second
#define qwerty3 -> first
#define qwerty4 -> second
#define umap unordered_map
#define uset unordered_set
#define pii pair < ll , ll >
#define pq priority_queue
#define dbg(x) cerr << #x << ": " << x << '\n'

namespace FastRead
{
    char __buff[5000];ll __lg = 0 , __p = 0;
    char nc()
    {
        if(__lg == __p){__lg = fread(__buff , 1 , 5000 , stdin);__p = 0;if(!__lg) return EOF;}
        return __buff[__p++];
    }
    template<class T>void read(T&__x)
    {
        T __sgn = 1; char __c;while(!isdigit(__c = nc()))if(__c == '-')__sgn = -1;
        __x = __c - '0';while(isdigit(__c = nc()))__x = __x * 10 + __c - '0';__x *= __sgn;
    }
}

using namespace FastRead;
using namespace std;

const ll N = 1e5 + 10;
const ll M = 1e9 + 7;
const ld PI = acos(-1);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n , m;
vector < int > G[N];
bool deleted[N];
stack < int > st;
pii edg[N];

signed main()
{
	#ifndef ONLINE_JUDGE
		FastIO , FILES;
	#endif

    int i;

    cin >> n >> m;

    for(int i = 1 ; i <= m ; i++)
    {
        int x , y;
        cin >> x >> y;
        edg[i] = {x , y};
        G[x].pb(i);
        G[y].pb(i);
    }

    for(int i = 1 ; i <= n ; i++)
        if(G[i].size() % 2)
            return cout << "-1" , 0;

    st.push(1);
    vector < int > order;

    while(!st.empty())
    {
        int node = st.top();

        if(G[node].size() == 0)
        {
            order.pb(node);
            st.pop();
        }
        else if(deleted[G[node].back()])
        {
            G[node].pop_back();
        }
        else
        {
            int to = node ^ edg[G[node].back()].first ^ edg[G[node].back()].second;
            st.push(to);
            deleted[G[node].back()] = 1;
            G[node].pop_back();
        }
    }

    order.pop_back();
    for(auto i : order) cout << i << ' ';
    return 0;
}