#include<bits/stdc++.h>

using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
const int N = 100010;
const int M = 100010;
vector<int> v[N];
int a[M],b[M], arb[M], n, m;
void dfs(int);
bitset<N> viz;
int main()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
        f>>a[i]>>b[i];
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
    }
    dfs(1);
    for(int i=1;i<=n;i++)
    {
        int dr=v[i].size()-1,st=0;
        do
        {
            while(st<dr&&arb[v[i][st]])st++;
            while(st<dr&&!arb[v[i][dr]])dr--;
            if(st<dr){swap(v[i][st],v[i][dr]);st++;dr--;}
        }
        while(st<dr);
    }
    int nod=1;
    while(v[nod].size())
    {
        while(v[nod].size()&&arb[v[nod].back()]==2)v[nod].pop_back();
        if(v[nod].size())
        {
            int edge=v[nod].back();
            v[nod].pop_back();
            g<<nod<<' ';
            nod=a[edge]+b[edge]-nod;
            //g<<nod<<' ';
            arb[edge]=2;
        }
    }
    return 0;
}
void dfs(int nod)
{
    viz[nod]=1;
    for(auto edge:v[nod])
    {
        int vec=a[edge]+b[edge]-nod;
        if(!viz[vec])
        {
            arb[edge]=1;
            dfs(vec);
        }
    }
}