#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>
#include <fstream>
using namespace std;

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

const int nmax = 1e5 + 1;

vector <int> g[nmax], gt[nmax], compConexe[nmax];
stack <int> st;
int viz[nmax], nrComp;

void DFS1(int nod)
{
    viz[nod] = 1;
    for (auto i : g[nod]) 
        if (viz[i] == 0) 
            DFS1(i);
        
    st.push(nod);
}

void DFS2(int nod)
{
    viz[nod] = 2;
    compConexe[nrComp].push_back(nod);
    for (auto i : gt[nod]) 
        if (viz[i] == 1) 
            DFS2(i);
        
}

int main()
{


    int n, m;
    int x, y;
    fin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        fin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    for (int i = 1; i <= n; ++i)  // dfs pe graful normal din fiecare nod
        if (viz[i] == 0) 
            DFS1(i);

    while (!st.empty()) { // parcurgem stiva in ordine inversa si facem dfs pe gradul transpus
        int nod = st.top();
        if (viz[nod] == 1) {
            ++nrComp;
            DFS2(nod);
        }
        st.pop();
    }

    fout << nrComp << "\n";
    for (int i = 1; i <= nrComp; ++i) {
        for (int aux : compConexe[i])
            fout << aux << " ";
        fout << "\n";
    }
    return 0;
}