#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;

#define NMAX 100005
#define pb push_back

int N, M, x, y, i, CTC, Stiva[NMAX];
vector< int > G[NMAX], GT[NMAX], Comp[NMAX];
bool Used[NMAX];

inline void Df1( int Nod )
{
	Used[Nod] = true;
	for( vector< int >::iterator it = G[Nod].begin(); it != G[Nod].end(); ++it )
		if( !Used[*it] )
			Df1( *it );
	Stiva[ ++Stiva[0] ] = Nod;
}

inline void Df2( int Nod )
{
	Used[Nod] = true;
	Comp[CTC].pb( Nod );
	for( vector< int >::iterator it = GT[Nod].begin(); it != GT[Nod].end(); ++it )
		if( !Used[*it] )
			Df2( *it );
}

int main()
{
	freopen("ctc.in", "r", stdin);
	freopen("ctc.out", "w", stdout);
	
	scanf("%d%d", &N, &M );
	for( ; M--; )
	{
		scanf("%d%d", &x, &y );
		G[x].pb( y );
		GT[y].pb( x );
	}
	
	Stiva[0] = 0;
	memset( Used, false, sizeof(Used) );
	for( i = 1; i <= N; ++i )
		if( !Used[i] )
			Df1( i );
	memset( Used, false, sizeof(Used) );
	for( CTC = 0, i = Stiva[0]; i; --i )
		if( !Used[ Stiva[i] ] )
			++CTC, Df2( Stiva[i] );
	
	printf("%d\n", CTC );
	for( i = 1; i <= CTC; ++i )
	{
		for( vector< int >::iterator it = Comp[i].begin(); it != Comp[i].end(); ++it )
			printf("%d ", *it );
		printf("\n");
	}
	
	return 0;
}