#include <stdio.h>

#include <vector>
#include <algorithm>

const int MAXN = 1e5;
std::vector<int> fwd[MAXN];
std::vector<int> back[MAXN];

bool viz[MAXN];
int ctc[MAXN];

std::vector<int> topo;
void dfs( int u ) {
  viz[u] = true;
  for( int v : fwd[u] )
    if( !viz[v] )
      dfs( v );
  topo.push_back( u );
}

void paint( int u, int C ) {
  ctc[u] = C;
  for( int v : back[u] )
    if( ctc[v] == -1 )
      paint( v, C );
}

int main() {
  FILE *fin = fopen( "ctc.in", "r" );
  FILE *fout = fopen( "ctc.out", "w" );

  int n, m;
  fscanf( fin, "%d%d", &n, &m );
  for( int i = 0; i < m; i++ ){
    int a, b;
    fscanf( fin, "%d%d", &a, &b );
    a--; b--;
    fwd[a].push_back( b );
    back[b].push_back( a );
  }

  for( int i = 0; i < n; i++ )
    if( !viz[i] )
      dfs( i );
  std::reverse( topo.begin(), topo.end() );

  for( int i = 0; i < n; i++ )
    ctc[i] = -1;

  int nctc = 0;
  for( int u : topo )
    if( ctc[u] == -1 )
      paint( u, nctc++ );

  std::vector<std::vector<int>> comps(nctc);
  for( int i = 0; i < n; i++ )
    comps[ctc[i]].push_back( i );

  fprintf( fout, "%d\n", (int)comps.size() );
  for( auto &comp : comps ){
    for( int x : comp )
      fprintf( fout, "%d ", x + 1 );
    fputc( '\n', fout );
  }

  fclose( fin );
  fclose( fout );
  return 0;
}