#include <fstream>
#include <vector>

#define inf 1e9
#define NMAX 100004

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

///graful g repr prin liste de adiacenta
vector <int> g[NMAX];
///graful transpus gt repr prin liste de adiacenta
vector <int> gt[NMAX];
bool viz[NMAX];

vector <int> ctc[NMAX];
int post[NMAX];

/// int nr; ///nr de comp tare conexe
int n,m,i,j,x,y,c,nr,poz;

void DFS(int x);
void DFST(int x);

int main()
{
    ///citire
    cin>>n>>m;
    for(i=1; i<=m; i++)
    {
        cin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    ///parcurg DFS graful g retinand varfurile in postordine
    for(i=1; i<=n; i++)
    {
        if(viz[i]==0)
        {
            DFS(i);
        }
    }

    ///parcurg vectorul postordine de la dr la st si fac DFST in graful transpus
    for(i=n;i>=1;i--)
    {
        ///in viz toate elem au val 1
        if(viz[post[i]]==1) ///acest vf este nevizitat in GT
        {
            nr++;
            DFST(post[i]);
        }
    }

    ///afisare
    cout<<nr<<'\n';
    for(i=1;i<=nr;i++)
    {
        for(j=0;j<ctc[i].size();j++)
        {
            cout<<ctc[i][j]<<' ';
        }
        cout<<'\n';
    }

    return 0;
}

void DFS(int x)
{
    int i;
    viz[x]=1;
    ///parcurg lista de adiacenta a lui x
    for(i=0; i<g[x].size(); i++)
    {
        if(viz[g[x][i]]==0)
        {
            DFS(g[x][i]);
        }
    }
    post[++poz]=x;
}

void DFST(int x)
{
    int i;
    viz[x]=0;
    ///retin acest vf in componenta conexa curenta
    ctc[nr].push_back(x);
    ///parcurg lista de adiacenta a lui x
    for(i=0; i<gt[x].size(); i++)
    {
        if(viz[gt[x][i]]==1)
        {
            DFST(gt[x][i]);
        }
    }
}