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

FILE *f=fopen("ciclueuler.in","r"),*g=fopen("ciclueuler.out","w");

const int maxn=100005;
int n,m,i,a,b,grad[maxn],k,coada[maxn];
bool viz[maxn],valid;
vector <int> x[maxn],afis;
stack <int> E;

void bf(int nod)
{
    int inc=1,sf=1;
    coada[1]=nod;
    while(inc<=sf)
    {
        nod=coada[inc];
        for(i=0;i<x[nod].size();viz[x[nod][i]]=true , i++)
            if(viz[x[nod][i]]==false)
                coada[++sf]=x[nod][i];
        inc++;
    }
}

int search(int a,int b)
{
    for(int i=0;i<x[b].size();i++)
        if(x[b][i]==a)
            return i;
}

void del(int a,int b)
{
    x[a].erase(x[a].begin());
    x[b].erase(x[b].begin()+search(a,b));
}

void expand(int nod)
{
    while(x[nod].size())
    {
        E.push(x[nod][0]);
        del(nod,x[nod][0]);
        nod=E.top();
    }
}

void write()
{
    vector <int>::iterator it;
    for(it=afis.begin()+1;it<afis.end();it++)
        fprintf(g,"%d ",*it);
    fprintf(g,"\n");
}

void read()
{
    fscanf(f,"%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        fscanf(f,"%d%d",&a,&b);
        x[a].push_back(b);
        x[b].push_back(a);
        grad[a]++;
        grad[b]++;
    }
    valid=true;
    bf(1);
    for(i=1;i<=n;i++)
        if(viz[i]==false||grad[i]%2==1)
            break;
    if(i<=n)
        valid=false;
    if(valid==true)
    {
        E.push(1);
        while(!E.empty())
        {
            expand(E.top());
            afis.push_back(E.top());
            E.pop();
        }
        write();
    }
    else
        fprintf(g,"-1\n");
}

int main()
{
    read();
    return 0;
}