#include<fstream>
#include<vector>
#include<algorithm>
 
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
 
vector <int> lvg[100001];
vector <int> lvgt[100001];

int d[100001], n, m, t;
 
int timp[100001],viz[100001];

vector <int> comp[100001];
  
void dfs(int nod)
{
    t++;
    viz[nod] = 1;
    int j, s;
    s = lvg[nod].size() - 1;
     
    for( j = 0; j <= s; j++ )
        if( !viz[lvg[nod][j]] )
			dfs(lvg[nod][j]);
    t++;
    timp[nod] = t;
}
void dfs2(int nod)
{
    viz[nod]=1;
    int j,s;
    comp[t].push_back(nod);
    s=lvgt[nod].size()-1;
     
    for(j=0;j<=s;j++)
        if( !viz[lvgt[nod][j]] )
			dfs2(lvgt[nod][j]);
}
 
bool cmp(int i,int j)
{ 
    return timp[i]>timp[j];
}
 
int main()
{
     
    int x,y,i;
     
    f>>n>>m;
     
    for( i = 1; i <= m; i++ )
        {
            f>>x>>y;
            lvg[x].push_back(y);
            lvgt[y].push_back(x);
        }
    for(i=1;i<=n;i++)
        if(!viz[i])dfs(i);
         
     
     
    for(i=1;i<=n;i++)
        {
            d[i]=i;
            viz[i]=0;
        }
    sort(d+1,d+n+1,cmp);
    t=0;
     
    for(i=1;i<=n;i++)
        {
             
            if(!viz[d[i]])
            {
                
                dfs2(d[i]);
            }
        }   
     
     
     
    g<<t<<"\n";
    for(i=1;i<=t;i++)
    {
        for(int j=0;j<=comp[i].size()-1;j++)
            g<<comp[i][j]<<" ";
        g<<"\n";
    }
    return 0;
}