#include <iostream>
#include <fstream>
#include <vector>
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],afis[maxn],k,copi;
bool viz[maxn],valid,in;
vector <int> x[maxn];

void df(int nod)
{
    viz[nod]=true;
    if(grad[nod]%2==1)
        valid=false;
    for(int i=0;i<x[nod].size();i++)
        if(viz[x[nod][i]]==false)
            df(x[nod][i]);
}

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

void build()
{
    int nod=1,s=m;
    afis[++k]=nod;
    while(s)
    {
        in=false;
        for(i=0;i<x[nod].size();i++)
            if(x[nod][i]!=1)
            {
                copi=x[nod][i];
                afis[++k]=x[nod][i];
                x[nod].erase(x[nod].begin()+i);
                x[copi].erase(x[copi].begin()+search(copi,nod));
                s--;
                nod=copi;
                in=true;
                break;
            }
        if(in==false)
        {
            //afis[++k]=1;
            s--;
        }
    }
}

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;
    df(1);
    for(i=1;i<=n;i++)
        if(viz[i]==false)
            break;
    if(i<=n)
        valid=false;
    if(valid==true)
        build();
}

void write()
{
    for(i=1;i<=k;i++)
        fprintf(g,"%d ",afis[i]);
    fprintf(g,"\n");
}

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