#include <fstream>
#include <vector>
#include <stack>
#include <list>
#include <algorithm>

using namespace std;

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

const int Nmax = 100005;

list<int> A[Nmax];

bool euler (int n)
{
    for (int i = 1; i <= n; i++)
        if (A[i].size() % 2)
            return false;
    return true;
}

void solve (int nod, stack<int>&stk)
{
    while (A[nod].size())
    {
        int nod_vecin = A[nod].back();
        A[nod].pop_back();
        A[nod_vecin].erase(find(A[nod_vecin].begin(), A[nod_vecin].end(), nod));
        solve(nod_vecin, stk);
    }
    stk.push(nod);
}

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

    stack<int> stk;

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;

        A[x].push_back(y);
        A[y].push_back(x);
    }

    if (!euler(n))
    {
        out << -1;
        return 0;
    }

    solve(1, stk);
    while (!stk.empty())
    {
        out << stk.top() << ' ';
        stk.pop();
    }
    return 0;
}