#include <iostream>
#include <cstdio>
#include <stack>
#include <vector>
#include <cstring>
using namespace std;
FILE *f=fopen("ctc.in","r");
vector <int> lv[100020];
vector <int> lvt[100020];
int n,m;
int used[100020];
stack <int> s;
void citire( )
{
    fscanf(f,"%d%d",&n,&m);
    int x,y;
    for(int i=1;i<=m;i++)
    {
        fscanf(f,"%d%d",&x,&y);
        lv[x].push_back(y);
        lvt[y].push_back(x);
    }
}
void dfs(int nc)
{
    used[nc]=1;
    vector <int> :: iterator ii;

    for(ii=lv[nc].begin();ii!=lv[nc].end();ii++)
        if(!used[*ii])
           dfs(*ii);

    s.push(nc);
}
int k;
vector <int> r[100020];
void dfs1(int nc)
{
    r[k].push_back(nc);
    used[nc]=1;
    vector <int> :: iterator ii;
      for(ii=lvt[nc].begin();ii!=lvt[nc].end();ii++)
        if(!used[*ii])
           dfs1(*ii);
}
void rezolvare( )
{
    for(int i=1;i<=n;i++)
        if(used[i]==0)
            dfs(i);
    memset(used,0,sizeof(used));
    while(!s.empty())
    {
        int nc=s.top();
        s.pop( );
        if(!used[nc])
        {
            k++;
            dfs1(nc);
        }
    }

}
int main()
{
    citire( );
    rezolvare( );
    FILE *f1=fopen("ctc.out","w");
    fprintf(f1,"%d",k);
    fprintf(f1,"\n");
    for(int i=1;i<=n;i++)
    {
        vector <int> :: iterator ii;
        for(ii=r[i].begin();ii!=r[i].end();ii++)
            fprintf(f1,"%d ",*ii);
            fprintf(f1,"\n");
    }
}