#include<cstdio>
#include<vector>
#include<queue>
using namespace std;
FILE*in=fopen("ciclueuler.in","r");
FILE*out=fopen("ciclueuler.out","w");
int n,m,x,y,i,grad[100005],ct;
bool use[500005];
struct muchie
{
    int nr;
    int nrord;
};
muchie z;
queue<muchie> v[100005];
void euler(int nod)
{
    while(grad[nod]>0)
    {
        if(use[v[nod].front().nrord]==0)
        {
            grad[nod]--;
            grad[v[nod].front().nr]--;
            use[v[nod].front().nrord]=1;
            euler(v[nod].front().nr);
        }
        v[nod].pop();
    }
    ct++;
    if(ct<=m)
    {
        fprintf(out,"%d ",nod);
    }
}
int main()
{
    fscanf(in,"%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        fscanf(in,"%d%d",&x,&y);
        z.nr=y;
        z.nrord=i;
        v[x].push(z);
        grad[x]++;
        z.nr=x;
        v[y].push(z);
        grad[y]++;
    }
    euler(1);
}