#include <fstream>
#include <vector>
#include <stack>
using namespace std;

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

int n,m;
vector<int>sol,d;
vector<vector<int>>g;

void citire()
{
    cin>>n>>m;
    g.resize(n+1);
    d.resize(n+1);
    int x,y;
    for(int i=0; i<m; i++)
    {
        cin>>x>>y;
        d[y]++;
        g[x].push_back(y);
    }
}
void ciclu()
{
    stack<int>s;
    s.push(1);
    while(!s.empty())
    {
        int nod=s.top();
        s.pop();
        while(g[nod].size())
        {
            s.push(g[nod].back());
            g[nod].pop_back();
        }
        sol.push_back(nod);
    }
}
int main()
{
    citire();
    for(int i=1;i<=n;i++)
        if(!d[i] || d[i]%2)
    {
        cout<<-1;
        return 0;
    }
    ciclu();
    for(auto x:sol)
        cout<<x<<' ';
    return 0;
}