#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
using namespace std;
int in(){
char c=getchar_unlocked();
while(c<'0'||c>'9')
c=getchar_unlocked();
int r=0;
while(c>='0'&&c<='9') {
r=r*10+c-'0';
c=getchar_unlocked();
}
return r;
}
void out(int x) {
int lz=0, r=0;
while(x%10==0) {
++lz;
x/=10;
}
while(x) {
r=r*10+x%10;
x/=10;
}
while(r) {
putchar_unlocked('0'+r%10);
r/=10;
}
while(lz--)
putchar_unlocked('0');
}
int vised[500001];
int vis[500001];
vector<pair<int,int>>adj[500001];
stack<int> s;
vector<vector<int>> all;
int str= 0;
void dfs(int i){
s.push(i);
if(vis[i]){
vector<int>a;a.push_back(s.top());
s.pop();
while(s.top()!=i){
a.push_back(s.top());
s.pop();
}
all.push_back(a);
str = a.size()-1;
return;
}
vis[i] =1;
for(auto j:adj[i]){
if(vised[j.second])continue;
vised[j.second] = 1;
dfs(j.first);
if(str){
vis[i] =0;
str--;
return ;
}
}
vis[i] = 0;
if(s.size())s.pop();
}
signed main(){
int n = in();int m=in();
for(int i = 0;i<m;i++){
int a=in();int b=in();
adj[a].push_back({b,i});
adj[b].push_back({a,i});
}
for(int i = 1;i<=n;i++){
dfs(i);
}
for(auto i:all){
for(auto j:i){out(j);putchar_unlocked(' ');}
putchar_unlocked('\n');
}
return 0;
}
