#include <bits/stdc++.h>


using namespace std;

int n, m, f[50001], f2[50001], cnt = 0, f3[50001], componenta[50001];
vector<int>G[50001], lista[50001], S, GT[50001];

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

void dfs(int nod)
{
    f[nod] = 1;
    for(auto x : G[nod])
        if(!f[x])
            dfs(x);
    S.push_back(nod);
}

void dfs2(int nod)
{
    lista[cnt].push_back(nod);
    f2[nod] = 1;
    for(auto x : GT[nod])
        if(!f2[x])
            dfs2(x);
}

int main()
{
    fin >> n >> m;
    while(m--)
    {
        int i, j; fin >> i >> j;
        G[i].push_back(j);
        GT[j].push_back(i);
    }
    for(int i = 1; i <= n; i++)
        if(!f[i])
            dfs(i);
    for(vector<int> :: reverse_iterator it = S.rbegin(); it != S.rend(); it++)
    {
        int nod = *it;
        if(f2[nod] == 0)
        {
            cnt++;
            dfs2(nod);
        }
    }
    fout << cnt << '\n';
    for(int i = 1; i <= cnt; i++)
    {
        sort(lista[i].begin(), lista[i].end());
        for(auto x : lista[i])
            componenta[x] = i;


    }
    for(int i = 1; i <= n; i++)
    {
        if(f3[componenta[i]] == 0)
        {
            f3[componenta[i]] = 1;
            int  j = componenta[i];
            fout << lista[j].size() << " ";
            for(auto x : lista[j])
                fout << x << " ";
            fout << '\n';
        }
    }
    return 0;
}