#include <fstream>
#include <vector>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n,m,x,y;
vector <int> G[100000];
vector <int>::iterator it;

void erasePoint(int t,int s)
{
    for(it = G[t].begin(); it != G[t].end(); ++it)
    {
        if(*it == s)
        {
            G[t].erase(it);
            break;
        }
    }
}
void DFS(int nod)
{
    for(int i = 0; i < G[nod].size(); i++)
    {
        int vecin = G[nod][i];

        erasePoint(nod,vecin);
        erasePoint(vecin,nod);
        DFS(vecin);
        g << vecin << " " << nod << " ";
    }

}

int main()
{
    f>>n>>m;
    while(m--)
    {
        f>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    DFS(1);
    return 0;
}