/**
 * Code by Patrick Sava
 * "Spiru Haret" National College of Bucharest
 **/

# include "fstream"
# include "cstring"
# include "vector"
# include "queue"
# include "bitset"
# include "algorithm"
# include "map"
# include "set"
# include "unordered_map"
# include "deque"
# include "string"
# include "iomanip"
# include "cmath"
# include "stack"
# include "cassert"

const char IN [ ] =  "ctc.in" ;
const char OUT [ ] = "ctc.out" ;

using namespace std ;

# define pb push_back
# define mp make_pair
# define FORN( a , b , c ) for ( register int a = b ; a <= c ; ++ a )
# define FORNBACK( a , b , c ) for ( register int a = b ; a >= c ; -- a )

ifstream cin ( IN ) ;
ofstream cout ( OUT ) ;

const int MAX = 1e5 + 14 ;

vector < int > gr [ MAX ] ;
vector < int > inv [ MAX ] ;

bitset < MAX > viz ;

vector < int > descopera ;

int cate ;

vector < int > ctc [ MAX ] ;

inline void dfs ( int nod )
{
    viz [ nod ] = 1 ;
    for ( auto x : gr [ nod ] )
        if ( viz [ x ] == 0 )
            dfs ( x ) ;
    descopera.pb ( nod ) ;
}

inline void dfs2 ( int nod )
{
    ctc [ cate ].pb ( nod ) ;
    viz [ nod ] = 0 ;
    for ( auto x : inv [ nod ] )
        if ( viz [ x ] == 1 )
            dfs2 ( x ) ;
}

int main()
{
    int n , m ;
    cin >> n >> m ;
    while ( m -- )
    {
        int x , y ;
        cin >> x >> y ;
        gr [ x ].pb ( y ) ;
        inv [ y ].pb ( x ) ;
    }
    FORN ( i , 1 , n )
        if ( !viz [ i ] ){
            dfs ( i ) ;
        }
    reverse ( descopera.begin() , descopera.end() ) ;
    for ( auto x : descopera )
        if ( viz [ x ] ) {
            ++ cate ;
            dfs2 ( x ) ;
        }
    cout << cate << '\n' ;
    FORN ( i , 1 , cate ){
        for ( auto x : ctc [ i ] )
            cout << x << ' ' ;
        cout << '\n' ;
    }
    return 0;
}