#include <bits/stdc++.h>
#define len(x) (int)(x).size()
#define range(i, x, y) for(int i=x; i<y; i++)
#define sws ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define vint vector<int>
#define vll vector<long long>
#define vstr vector<string>
#define ll long long
#define F first
#define S second
#define pb push_back
#define pf push_front
#define del(a, n) (a).erase(a.begin()+(n))
#define mp make_pair
#define all(a) (a.begin(), a.end())
const int MAX = 1e6;
using namespace std;
void hier(unordered_set<int> gra[], int n, int m, int now){
int next = now;
stack<int> path;
vint sol;
int value_edge[n+1];
for(int i = 0; i <= n; i++){
value_edge[i] = gra[i].size();
}
path.push(now);
while(!path.empty()){
if(value_edge[now]){
path.push(now);
for(auto x : gra[now]){
next = x;
break;
}
gra[now].erase(next);
gra[next].erase(now);
value_edge[now] --;
value_edge[next] --;
now = next;
} else{
sol.push_back(now);
now = path.top();
path.pop();
}
}
for(int i = sol.size()-1; i >= 0; i--){
cout << sol[i] <<" ";
}
}
int main(){
sws
int n, m;
cin >> n >> m;
unordered_set<int> gra[n+1];
for(int i=0; i<m; i++){
int u, v;
cin >> u >> v;
gra[u].insert(v);
gra[v].insert(u);
}
while(1){
int term = 0;
int check = 2;
for(int i=1; i <= n; i++){
for(auto x : gra[i]){
term = x;
check = 1;
break;
}
if(check == 1)
break;
}
if(term){
hier(gra, n, m, term);
cout << "\n";
} else return 1;
}
}
