#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define tiii tuple<int,int,int>
using namespace std;
int main(){
int n, m;
cin >> n >> m;
vector<set<int>> adj(n);
for(int i = 0; i < m; i++){
int a,b;
cin >> a >> b;
a--;b--;
adj[a].insert(b);
adj[b].insert(a);
}
vector<int> trav;
stack<int> S;
S.push(0);
while(S.size()){
int v = S.top();
if(adj[v].size() == 0){
S.pop();
trav.push_back(v);
}else{
int u = *adj[v].begin();
adj[u].erase(v);
adj[v].erase(u);
S.push(u);
}
}
set<int> occ;
for(int i = 0; i < trav.size(); i++){
if(occ.count(trav[i])){
occ.clear();
cout << "\n";
}
cout << trav[i]+1 << " ";
//occ.insert(trav[i]);
}
}
