#include <fstream>
#include <vector>
#define Dmax 100005
using namespace std;
 
ifstream intrare("ciclueuler.in");
ofstream iesire("ciclueuler.out");
 
int n, m;
int d[Dmax];
int viz[Dmax];
vector<int>G[Dmax];
int total;
struct nod{int vf; struct nod * urm;};
typedef struct nod * Lista;
Lista C1, C2, sfC1, sfC2;
 
void citire();
void dfs(int x);
void determinare_eulerian();
bool conex();
bool gradepare();
int ciclu(int x, Lista &inc, Lista &sf);
void afisare();
 
int main()
{
    citire();
    if (conex() && gradepare())
    {
        determinare_eulerian();
        afisare();
    }
    else
        iesire <<-1<<'\n';
    iesire.close();
    return 0;
}
void citire()
{
    int x, y, i;
    intrare>>n>>m;
    for(i=1;i<=m;i++)
    {
        intrare>>x>>y;
        d[x]++; d[y]++;
        G[x].push_back(y);
        G[y].push_back(x);
    }
}
void dfs(int x)
{
    int i;
    viz[x]=true;
    for(i=0;i<int(G[x].size());i++)
        if(!viz[G[x][i]])
            dfs(G[x][i]);
}
bool gradepare()
{
    int i;
    for(i = 1; i <= n; i++)
        if (d[i]%2)
            return 0;
    return 1;
}
bool conex()
{
    int x,i;
    for(x=1;x<=n&&!d[x];x++);
        if(x>=n)
            return 0;
        dfs(x);
        for(i=1;i<=n;i++)
            if(!viz[i]&&d[i])
                return 0;
    return 1;
}
void determinare_eulerian()
{
    int x,nr2;
    Lista p,q;
    for(x=1;x<=n&&!d[x];x++);
    total=ciclu(x,C1,sfC1);
    while(total!=m)
    {
        for(p=C1;!d[p->vf];p=p->urm);
        nr2=ciclu(p->vf,C2,sfC2);
        q=p->urm;
        p->urm=C2->urm;
        sfC2->urm=q;
        total+=nr2;
    }
}
int ciclu(int x, Lista &inc, Lista &sf)
{
    Lista p;
    int y,uvf,i,j,lg = 0;
    p=new nod;
    p->vf=x;
    p->urm=NULL;
    inc=sf=p;
    do
    {
        uvf=sf->vf;
        for(i=0;i<int(G[uvf].size());i++)
            if(G[uvf][i])
                break;
        y=G[uvf][i];
        p=new nod;
        p->vf=y;
        p->urm=NULL;
        sf->urm=p;
        sf=p;
        lg++;
        G[uvf][i]=0;
        for(j=0;j<int(G[y].size());j++)
            if(G[y][j]==uvf)
            {
                G[y][j]=0;
                break;
            }
        d[uvf]--;d[y]--;
    }
    while(y!=x);
    return lg;
}
void afisare()
{
    Lista p;
    for(p=C1; p;p=p->urm)
        iesire<<p->vf<<' ';
    iesire<<'\n';
}