#include <fstream>
#include <vector>
#include <stack>
#define oo 1111111

using namespace std;

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

bool vm[500005];
vector< pair<int, int> > L[100005];
vector< pair<int, int> > M[500005];
stack<int> s;

vector<int> ans;

void df(int v) {
    for(int i = 0; i < L[v].size(); i ++) {
        int cur = L[v][i].first;
        int muc = L[v][i].second;
        if(!vm[muc]) {
            vm[muc] = true;
            df(cur);
        }
    }
    ans.push_back(v);
}

int main()
{
    int n, m, x, y; f >> n >> m;
    for(int i = 0; i < m; i ++) {
        f >> x >> y;
        L[x].push_back({y, i});
        L[y].push_back({x, i});
        M[i].push_back({x, y});
    }

    for(int i = 1; i <= n; i ++) {
        if(L[i].size() & 1) {
            g << "-1\n";
            return 0;
        }
    }

    df(1);
    if(ans.size() != m + 1) {
        g << "-1\n";
        return 0;
    }
    for(int i = ans.size() - 1; i > 0; i --) g << ans[i] << " ";
    g << "\n";
    return 0;
}