#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "algo/debug.h"
#else
#define debug(...) 42
#endif
#define fr first
#define sc second
#define mp make_pair
#define pb push_back
#define pf push_front
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(), x.rend()
using ll = long long;
using ull = unsigned long long;
using str = string;
using pii = pair<int,int>;
using pll = pair<long long, long long>;
const int nax = 500'001;
vector<int>flag(nax);
vector<vector<pair<int,int>>>adj(nax);
vector<int>pracka;
inline int readint(){
int ret=0;
for(char c;;){
c=getchar_unlocked();
if('0'<=c and c<='9')
ret=ret*10+(c&15);
else
return ret;
}
}
vector<char> digits;
inline void printint(int x){
do{
digits.push_back(x%10|48);
x/=10;
}while(x);
while(not digits.empty())
putchar(digits.back()), digits.pop_back();
}
void Euler(int v){
for (pii& x : adj[v]){
if (flag[x.sc])continue;
flag[x.sc] = 1;
Euler(x.fr);
}
pracka.pb(v);
}
void solve(){
int n = readint();
int m = readint();
for (int i = 0; i < m; i++){
int a,b;
a = readint();
b = readint();
--a,--b;
adj[a].pb({b,i});
adj[b].pb({a,i});
}
Euler(0);
int r = -1;
vector<vector<int>>cycles;
vector<int>visited(n + 1);
stack<int>c;
while(r < (int)pracka.size()){
++r;
if (visited[pracka[r]]){
cycles.push_back(vector<int>());
cycles.back().push_back(pracka[r]);
while(c.top() != pracka[r]){
visited[c.top()] = 0;
cycles.back().push_back(c.top());
c.pop();
}
}else{
c.push(pracka[r]);
visited[pracka[r]] = 1;
}
}
for (int i = 0; i < (int)cycles.size() - 1; i++){
for (int j : cycles[i]){
printint(j + 1);
putchar(' ');
}
putchar('\n');
}
}
int main(){
solve();
return 0;
}
