#include <algorithm>
#include <fstream>
#include <vector>

using namespace std;

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

vector <vector <int> > a;
vector <int> x;

void read()
{
    int n,m;
    cin >> n >> m;
    a.resize(n+1);
    for (int i=0,x,y; i<m; i++)
    {
        cin >> x >> y;
        if (count(a[x].begin(),a[x].end(),y)==0) a[x].push_back(y);
    }
    cin.close();
}

void eul(int v)
{
    x.push_back(v);
    for (int i=0; i<x.size(); i++)
    {
        for (int j=0; j<a[x[i]].size(); j++)
            x.push_back(a[x[i]][j]);
        a[x[i]].clear();
    }
}

void write()
{
    if (x.size()<2) cout << "-1"; else
    for (int i=0; i<x.size(); i++)
        cout << x[i] << ' ';
    cout.close();
}

main()
{
    read();
    for (int i=1; i<a.size(); i++)
        if (a[i].size()!=0) {eul(i);break;}
    write();
}