#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
#define nmax 100005
int n, m, x, y;
vector<int> v[nmax];
queue<int> q;
void euler(int nod) {
    while (!v[nod].empty()) {
        int w = v[nod].back();
        v[nod].pop_back();
        for (int i = 0; i < v[w].size(); ++i)
            if (v[w][i] == nod) { swap(v[w][i],v[w][v[w].size()-1]); v[w].pop_back(); break;}
        euler(w);
    }
    q.push(nod);
}

int main()
{
    f >> n >> m;
    for (int i = 1; i <= m; ++i) {
        f >> x >> y;
        v[x].push_back(y), v[y].push_back(x);
    }
    for (int i = 1; i <= n; ++i)
        if (v[i].size() & 1) { g << "-1\n"; return 0; }
    euler(1);
    while (q.size() - 1) { g << q.front() << ' '; q.pop(); }
    return 0;
}