#include <bits/stdc++.h>
#define DIM 50001

using namespace std;

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

int n, m, i, j, x, y, k, nrCtc;
int f[DIM], isStec[DIM], niv[DIM], low[DIM], ind[DIM];

vector <int> L[DIM], comp[DIM];

stack <int> stec;

void dfs (int nod){
    int don, vecin;
    f[nod] = 1;
    stec.push(nod), isStec[nod] = 1;
    low[nod] = niv[nod] = ++k;
    for (int i=0; i<L[nod].size(); i++){
        vecin = L[nod][i];
        if (!f[vecin]){
            dfs(vecin);
            low[nod] = min (low[nod], low[vecin]);
        }
        else{
            if (isStec[vecin]){
                low[nod] = min (low[nod], low[vecin]);
            }
        }
    }
    if (low[nod] == niv[nod]){
        nrCtc++;
        do{
            don = stec.top();
            stec.pop();
            isStec[don] = 0;
            comp[nrCtc].push_back(don);
        }while (nod != don);
    }
}

bool cmp (int &a, int &b){
    return comp[a][0] < comp[b][0];
}

int main()
{
    fin >> n >> m;
    for (i=1; i<=m; i++){
        fin >> x >> y;
        L[x].push_back(y);
    }
    for (i=1; i<=n; i++){
        if (!f[i]){
            dfs(i);
        }
    }
    for (i=1; i<=nrCtc; i++){
        sort (comp[i].begin(), comp[i].end());
        ind[i] = i;
    }
    sort (ind + 1, ind + nrCtc + 1, cmp);
    fout << nrCtc << "\n";
    for (i=1; i<=nrCtc; i++){
        fout << comp[ind[i]].size() << " ";
        for (j=0; j<comp[ind[i]].size(); j++){
            fout << comp[ind[i]][j] << " ";
        }
        fout << "\n";
    }
    return 0;
}