#include <iostream>
#include <fstream>
#include <vector>
#define Nmax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector  <int>P[Nmax];
vector  <int>I[Nmax];
vector  <int>Sol[Nmax];
int N,M,k,K,O[Nmax],Use[Nmax],Use1[Nmax];
void read()
{
    fin>>N>>M;
    for(int i=1;i<=M;i++)
    {
        int a,b;
        fin>>a>>b;
        P[a].push_back(b);
        I[b].push_back(a);
    }
}
void DFSS(int Nod)
{
    Use1[Nod] = 1;
    for(int i = 0; i< (int)P[Nod].size(); i++)
    {
        int Vecin = P[Nod][i];
        if(!Use1[Vecin])
        {
            DFSS(Vecin);
        }
    }
    O[++k] = Nod;
}
void DFSC(int Nod)
{
    Use[Nod] = 1;
    Sol[K].push_back(Nod);
    for(int i = 0; i< (int)I[Nod].size(); i++)
    {
        int Vecin = I[Nod][i];
        if(!Use[Vecin])
        {
            DFSC(Vecin);
        }
    }
}
void solve()
{
    for(int i=1;i<=N;i++)
    {
        if(!Use1[i])
            DFSS(i);
    }
    for(int i=N;i>=1;i--)
    {
        if(!Use[O[i]])
        {
            K++;
            DFSC(O[i]);
        }
    }
}
void print()
{
    fout<<K;
    for(int i=1;i<=K;i++)
    {
        fout<<"\n";
        for(int j=0;j<Sol[i].size();j++)
            fout<<Sol[i][j]<<" ";
    }
    fout<<"\n";
}
int main()
{
    read();
    solve();
    print();
    return 0;
}