#include <iostream>
#include <cstdio>

using namespace std;

int m,n,k;

struct nod
{
    int inf;
    nod*a;
}*p[100010];
int nr_nod[100010];

void adn(int x,int y)
{
    nod*c=new nod;
    c->inf=y;
    c->a=p[x];
    p[x]=c;
}

void ster(int y,int x)
{
    if(p[x]->inf==y)
            p[x]=p[x]->a;
    else
    {
        nod*aux;
        aux=p[x];
        for(nod*c=p[x]->a; c!=NULL; c=c->a,aux=aux->a)
            if(c->inf==y)
            {
                c->a=aux;
                break;
            }
    }
}

void par(int x)
{
    nr_nod[++k]=x;
    if(p[x]!=NULL)
    {
        int aux=p[x]->inf;
        p[x]=p[x]->a;
        ster(x,aux);
        par(aux);
    }
}

int ver()
{
    for(int i=1; i<=n; i++)
        if(nr_nod[i]%2==1)
            return 0;
    return 1;
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d",&n,&m);
    int x,y;
    for(int i=1; i<=m; i++)
    {
        scanf("%d %d",&x,&y);
        //cout<<x<<y<<endl;
        adn(x,y);
        nr_nod[x]++;
        if(x!=y)
        {
            nr_nod[y]++;
            adn(y,x);
        }
    }
    if(ver())
        printf("-1");
    else
    {
        for(int i=1; i<=n; i++)
            nr_nod[i]=0;
        par(1);
        for(int i=1; i<k; i++)
            printf("%d ",nr_nod[i]);
    }
    return 0;
}