#include <bits/stdc++.h>
#define ll long long
#define sz(v) (int)v.size()
using namespace std;

const int NMAX = 1e5 + 5;
vector<int> graf[NMAX];
vector<int> ans;
bool used[5 * NMAX];
int from[5 * NMAX], to[5 * NMAX], n, m;

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

void dfs(int nod) {
    while(!graf[nod].empty()) {
        int p = graf[nod].back();
        graf[nod].pop_back();

        if(!used[p]) {
            used[p] = true;

            if(to[p] == nod)
                dfs(from[p]);
            else
                dfs(to[p]);
        }
    }
    ans.push_back(nod);
}

int main() {
    //ifstream fin("date.in.txt");
    fin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        int a, b;
        fin >> a >> b;
        graf[a].push_back(i);
        graf[b].push_back(i);
        from[i] = a;
        to[i] = b;
    }

    for (int i = 1; i <= n; ++i) {
        if(sz(graf[i]) % 2 == 1) {
            fout << -1;
            return 0;
        }
    }

    dfs(1);

    for (int x : ans)
        fout << x << " ";

    return 0;
}