#include <iostream>
#include <fstream>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n,m,x,y,k,gr[100001],sir[100002];
struct muchie{int b;muchie *n;}*a[100001],*p;
bool v[100001];
void delet(int x,int y)
{
    muchie *p=a[x];
    if(p->b!=y)
    {

        for(;p->n->b!=y&&p->n!=NULL;p=p->n)if(p->n==p)cout<<x<<' '<<y<<' '<<p->b<<'\n';;
        if(p->n==NULL){cout<<" '-' ";}
        else
        {
            p->n=p->n->n;
            p=p->n;
            delete p;
        }
    }
    else
    {
        a[x]=p->n;
        delete p;
    }
}
void srtitdii(int x)
{
    int B[19901];
    B[0]=x;x=1;
    p=a[B[x-1]];
    B[x]=p->b;
    if(p->b!=B[x-1])delet(p->b,B[x-1]);
    a[B[x-1]]=a[B[x-1]]->n;
    --gr[p->b];--gr[B[x-1]];
    delete p;
    ++x;
    while(B[x-1]!=B[0])
    {
        p=a[B[x-1]];
        B[x]=p->b;
        if(p->b!=B[x-1])delet(p->b,B[x-1]);
        a[B[x-1]]=a[B[x-1]]->n;
        --gr[p->b];--gr[B[x-1]];
        delete p;
        ++x;
    }
    B[x]=0;
    for(int i=1;1;++i)if(sir[i]==B[0])
    {
        ++i;
        int h=i,j;
        for(j=x;sir[i]!=0;++j,++i)
        {
            B[j]=sir[i];
        }
        B[j]=0;
        for(j=1;B[j]!=0;++j,++h)
        {
            sir[h]=B[j];
        }
		break;
    }
}
int main()
{
    f>>n>>m;
    for(int i=1;i<=n;++i)a[i]=NULL;
    while(f>>x>>y)
    {
        p=new muchie;
        p->b=x;
        p->n=a[y];
        a[y]=p;
        p=new muchie;
        p->b=y;
        p->n=a[x];
        a[x]=p;
        ++gr[x];++gr[y];
    }
    for(int i=1;i<=n;++i)if(gr[i]%2==1){g<<-1;return 0;}
    for(int i=1;1;++i)if(gr[i]!=0){sir[1]=i;srtitdii(i);break;}
    for(int i=1;i<=m;++i)if(gr[sir[i]]>0)
    {
        srtitdii(sir[i]);
    }
    for(int i=1;i<=m;++i)g<<sir[i]<<' ';
    return 0;
}