#include <iostream>
#include <fstream>
#include <list>
#include <stack>
#include <algorithm>
#define maxN 100005

using namespace std;

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

int n, m, Cycle[maxN], nr;
list <int> G[maxN];
stack <int> st;

void Remove (int x, int y) {
    G[x].erase(G[x].begin());
    G[y].erase(find(G[y].begin(), G[y].end(), x));
}

bool EulCheck () {
    for (int i = 1; i <= n; ++i) {
        if (G[i].size() & 1)
            return false;
    }
    return true;
}

void EulerUtil () {
    st.push(1);
    while (!st.empty()) {
        int x = st.top();
        if (G[x].size() == 0) {
            Cycle[++nr] = x;
            st.pop();
            continue;
        }
        int y = *G[x].begin();
        st.push(y);
        Remove(x, y);
    }
}

int main () {
    fin >> n >> m;
    int x, y;
    for (int i = 1; i <= m; ++i) {
        fin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
    }

    if (not EulCheck()) {
        cout << - 1;
        return 0;
    }

    EulerUtil();
    for (int i = nr; i >= 1; --i) {
        fout << Cycle[i] << " ";
    }
}