#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int n, m, start[100005], X[500005], Y[500005], d[100005];
vector<int> L[100005];
vector<int> sol;
bool viz[500005];
bool Este_Eulerian()
{
    for(int i = 1;i <= n;i++)
        if(d[i] % 2 > 0) return 0;
    return 1;
}
void Euler(int x)
{
    while(start[x] < L[x].size())
    {
        int muchie = L[x][start[x]];
        start[x]++;
        if(viz[muchie] == 0)
        {
            viz[muchie] = 1;
            Euler(X[muchie] + Y[muchie] - x);
        }
    }
    sol.push_back(x);
}

int main()
{
    int i, j;
    fin >> n >> m;
    for(int ind = 1;ind <= m;ind++)
    {
        fin >> i >> j;
        d[i]++;d[j]++;
        X[ind] = i;Y[ind] = j;
        L[i].push_back(ind);
        L[j].push_back(ind);
    }
    if(!Este_Eulerian())
    {
        fout << "-1\n";
        fout.close();
        return 0;
    }
    Euler(1);
    for(int e : sol)
        fout << e << " ";
    fout << "\n";
    fout.close();
    return 0;
}