#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");
vector<pair<int,int>>l[100005];
int n,m,grad[100005],viz[100005],sol[500005],k,viz_muchie[500005];
stack<int>s;
void dfs(int nod)
{
    viz[nod]=1;
    for(int i=0; i<l[nod].size(); i++)
    {
        int vecin=l[nod][i].first;
        if(viz[vecin]==0)
            dfs(vecin);
    }
}
void euler(int nod)
{
    s.push(nod);
    while(!s.empty())
    {
        int nod=s.top();
        while(!l[nod].empty() && viz_muchie[l[nod].back().second]==1)
            l[nod].pop_back();
        if(l[nod].empty())
        {
            s.pop();
            sol[++k]=nod;
        }
        else
        {
            viz_muchie[l[nod].back().second]=1;
            s.push(l[nod].back().first);
            l[nod].pop_back();
        }
    }
}
int main()
{
    cin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int a,b;
        cin>>a>>b;
        l[a].push_back({b,i});
        l[b].push_back({a,i});
        grad[a]++;
        grad[b]++;
    }
    dfs(1);
    for(int i=1; i<=n; i++)
        if(viz[i]==0 || grad[i]%2!=0)///daca nu e conex sau daca nu are toate nodurile cu grad par
        {
            cout<<-1;
            return 0;
        }
    euler(1);
    for(int i=1;i<=k-1;i++)
        cout<<sol[i]<<" ";
    return 0;
}