#include<bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;
unordered_set<int> adj[500100];
int deg[500100];
stack<int> sol;
void reverse(){
stack<int> temp;
while(sol.size())
temp.push(sol.top()), sol.pop();
sol = temp;
}
void print(){
stack<int> now;
bitset<500100> appeared;
while(sol.size()){
if(appeared[sol.top()]){
cout << sol.top() << ' ';
while(now.top()!=sol.top())
cout << now.top() << ' ', appeared[now.top()] = 0, now.pop();
cout << '\n';
} else {
appeared[sol.top()] = 1;
now.push(sol.top());
}
sol.pop();
}
}
void dfs(int n){
while(adj[n].size()){
int i = *adj[n].begin();
adj[n].erase(i);
adj[i].erase(n);
dfs(i);
}
sol.push(n);
}
int main(){
cin.sync_with_stdio(false);
cin.tie(nullptr);
cout.sync_with_stdio(false);
cout.tie(nullptr);
int n, m;
cin >> n >> m;
for(int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
adj[a].insert(b);
adj[b].insert(a);
deg[a]++;
deg[b]++;
}
dfs(1);
reverse();
print();
return 0;
}
