#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 < int , int >
#define pq priority_queue
#define dbg(x) cerr << #x << ": " << x << '\n'

namespace FastRead
{
    char buff[5000];int 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 int N = 5e5 + 10;
const int M = 1e9 + 7;
const ld PI = acos(-1);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n , m , x , y;
bool seen_edge[N];
int from[N] , to[N];
vector < int > g[N] , s , ans;

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

    int i;

    cin >> n >> m;

    for(i = 1 ; i <= m ; i++)
    {
        cin >> x >> y;

        g[x].pb(i);
        g[y].pb(i);

        from[i] = x;
        to[i] = y;
    }

    for(i = 1 ; i <= n ; i++)
        if(g[i].size() & 1)
            return cout << -1 , 0;

    s.pb(1);

    while(!s.empty())
    {
        int node = s.back();

        if(!g[node].empty())
        {
            int edge = g[node].back();
            int go = from[edge] ^ to[edge] ^ node;
            g[node].pop_back();

            if(!seen_edge[edge])
            {
                seen_edge[edge] = 1;
                s.pb(go);
            }
        }
        else
        {
            s.pop_back();
            ans.pb(node);
        }
    }

    for(i = 0 ; i < ans.size() - 1 ; i++)
        cout << ans[i] << ' ';

    return 0;
}