#include <iostream>
#include <fstream>
#include <list>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;

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

const int MAXN = 100005;
int n, m, ciclu[5 * MAXN];
list<int> g[MAXN];
stack<int> st;

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


int main()
{
    in >> n >> m;

    for (int i = 1, x, y; i <= m; ++i) {
        in >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }

    for (int i = 1; i <= n; ++i) {
        if (g[i].size() % 2 != 0) {
            out << -1; return 0;
        }
    }

    st.push(1);
    while (!st.empty()) {
        int x = st.top();
        if (g[x].size() == 0) {
            ciclu[++ciclu[0]] = x;
            st.pop();
            continue;
        }
        int y = *g[x].begin();
        st.push(y);
        remove_edge(x, y);
    }

    for (int i = ciclu[0]; i >= 1; --i) out << ciclu[i] << " ";

    return 0;
}