#include<fstream>
#include<vector>
#include<algorithm>

using namespace std;


vector <int> lvg[100001];
vector <int> lvgt[100001];
int d[100001];

int n,m,t;

int timp[100001],viz[100001];
ifstream fin("ctc.in");
ofstream fout("ctc.out");
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;

    fin>>n>>m;

    for(i=1;i<=m;i++)
        {
            fin>>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]])
            {
                ++t;
                dfs2(d[i]);
            }
        }



    fout<<t<<"\n";
    for(i=1;i<=t;i++)
    {
        for(int j=0;j<=comp[i].size()-1;j++)
            fout<<comp[i][j]<<" ";
        fout<<"\n";
    }
    return 0;
}