#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
// mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const int MAXN = 5e5 + 7 ;
bool used[ MAXN ] , aux[ MAXN ] ;
vector < int > v[ MAXN ] ;
pair < int , int > hh[ MAXN ] ;
vector < int > ord , stk ;
void dfs ( int x ) {
while ( v[ x ].empty ( ) == false ) {
int id = v[ x ].back ( ) ;
v[ x ].pop_back ( ) ;
if ( used[ id ] == false ) {
used[ id ] = true ;
dfs ( hh[ id ].first + hh[ id ].second - x ) ;
}
}
ord.push_back ( x ) ;
}
void solve ( ) {
int n , m ; cin >> n >> m ;
for ( int i = 1 , x , y ; i <= m ; ++ i ) {
cin >> x >> y ;
hh[ i ] = { x , y } ;
v[ x ].push_back ( i ) ;
v[ y ].push_back ( i ) ;
}
dfs ( 1 ) ;
for ( auto x : ord ) {
if ( aux[ x ] == false ) {
aux[ x ] = true ;
stk.push_back ( x ) ;
}
else {
cout << x ;
while ( stk.back ( ) != x ) {
int y = stk.back ( ) ; stk.pop_back ( ) ;
cout << " " << y ;
aux[ y ] = false ;
}
cout << "\n" ;
}
}
}
int main ( ) {
ios_base :: sync_with_stdio ( false ) ;
cin.tie ( NULL ) ;
int t = 1 ; // cin >> t ;
while ( t -- ) { solve ( ) ; }
return 0 ;
}
