#include <cstdio>
#include <vector>

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

int nod,muc;

const int Q=500001,W=100001;

struct muchie
{
    int x,y;
    bool f;
} v[Q];

int urm[Q],lst[W],nr,val[W];

void inline add(int i)
{
    nr++;
    val[nr]=i;
    urm[nr]=lst[v[i].x];
    lst[v[i].x]=nr;

    nr++;
    val[nr]=i;
    urm[nr]=lst[v[i].y];
    lst[v[i].y]=nr;
}

int viz=0;

void inline make(int act)
{
    int m;

    while(lst[act]!=0)
    {
        m=val[lst[act]];

        lst[act]=urm[lst[act]];

        while(v[m].f==1)
        {
            m=val[lst[act]];
            lst[act]=urm[lst[act]];
        }
        if(m==0)
            break;


        v[m].f=1;
        viz++;

        if(v[m].x==act)
        {
            fprintf(out,"%d ",v[m].y);
            act=v[m].y;
        }
        else
        {
            fprintf(out,"%d ",v[m].x);
            act=v[m].x;
        }


    }
}

int main()
{
    fscanf(in,"%d%d",&nod,&muc);

    int a,b;

    for(int i=1; i<=muc; i++)
    {
        fscanf(in,"%d%d",&v[i].x,&v[i].y);
        add(i);
    }

    make(1);

    while(viz!=muc)
    {
        for(int i=1; i<=nod; i++)
        {
            if(lst[i]!=0)
            {
                if(v[val[lst[i]]].f==1)
                {
                    lst[i]=urm[lst[i]];
                }
                else
                {
                    fprintf(out,"%d ",i);
                    make(i);
                }
            }
        }
    }



    return 0;
}