#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

const int NMAX = 100005;

stack < int > S;
vector < int > G[NMAX], GT[NMAX], CTC[NMAX];

int n, m, nrCTC;
int vis[NMAX];

void read()
{
    fin >> n >> m;
    for (int i = 1; i <= m; i++){
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS(int nod)
{
    vis[nod] = 1;
    for (unsigned int i = 0; i < G[nod].size(); i++){
        int vecin = G[nod][i];
        if (!vis[vecin])
            DFS(vecin);
    }
    S.push(nod); /// adaugam in stiva
}

void DFSM(int nod)
{
    vis[nod] = 2;
    CTC[nrCTC].push_back(nod);
    for (unsigned int i = 0; i < GT[nod].size(); i++){
        int vecin = GT[nod][i];
        if (vis[vecin] == 1)
            DFSM(vecin);
    }

}

void solve()
{
    for (int i = 1; i <= n; i++)
        if (!vis[i])
            DFS(i);

    while (!S.empty()){
        int nod = S.top();
        if (vis[nod] == 1){
            nrCTC++;
            DFSM(nod);
        }
        S.pop();
    }
}

void print()
{
    fout << nrCTC << "\n";
    for (int i = 1; i <= nrCTC; i++){
        for (unsigned int j = 0; j < CTC[i].size(); j++)
            fout << CTC[i][j] << " ";
        fout << "\n";
    }
}

int main()
{
    read();
    solve();
    print();
    return 0;
}