#include <bits/stdc++.h>

using namespace std;

    ifstream fin("ctc.in");
    ofstream fout("ctc.out");

vector <int> G[100005];
vector <int> Go[100005];
vector <int> Gi[100005];
vector <int> where;
vector <int> discovered;
vector <bool> used;

void DFP(const int n, vector <int> *G)
{
    vector <int> :: iterator it;

    used[n]=1;

    for(it=G[n].begin();it!=G[n].end();it++)
    {
        if(used[*it]==0)
            DFP(*it,G);
    }

    discovered.push_back(n);
}

void DFM(const int n, const int witch, vector <int> *G)
{
    vector <int> :: iterator it;

    where[n]=witch;

    for(it=G[n].begin();it!=G[n].end();it++)
    {
        if(where[*it]==0)
            DFM(*it,witch,G);
    }
}

int main()
{
    int n,m, cons=1,x,y;

    fin>>n>>m;

    for(int i=1; i <= m; i++)
    {
        fin>>x>>y;
        Go[x-1].push_back(y-1);
        Gi[y-1].push_back(x-1);
    }

    used.resize(n);
    used.assign(n,0);

    for(int i=0;i<n;i++)
        if(used[i]==0)
            DFP(i,Go);

    where.resize(n);
    where.assign(n,0);

    for(;discovered.size();discovered.pop_back())
        if(where[discovered.back()]==0)
            {
                DFM(discovered.back(),cons,Gi);
                cons++;
            }

    for(int i=0;i<n;i++)
        G[where[i]].push_back(i);


    vector <int> :: iterator it;


    fout<<cons-1<<'\n';

    for(int i=1;i<cons;i++)
    {
        for(it=G[i].begin();it!=G[i].end();it++)
            fout<<*it+1<<' ';
        fout<<'\n';
    }
}