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

using namespace std;

ifstream f ("ctc.in");
ofstream g ("ctc.out");

const int NMAX = 100000 + 1;

int n, m, index_crt, nrcomp;
int lowlink[NMAX], index[NMAX];
bool in_stack[NMAX];
stack <int> st;
vector <int> graf[NMAX];
vector < vector <int> > componente;

void citeste() {
    int a, b;
    f >> n >> m;

    for (int i = 1; i <= m; i++) {
        f >> a >> b;
        graf[a].push_back(b);
    }
}

void tarjan(int nod) {
    int l = graf[nod].size(), fiu, top;

    index[nod] = lowlink[nod] = ++index_crt;
    st.push(nod); in_stack[nod] = true;

    for (int i = 0; i < l; i++) {
        fiu = graf[nod][i];
        if (!index[fiu]) tarjan(fiu);
        if (in_stack[fiu]) lowlink[nod] = min(lowlink[nod], lowlink[fiu]);
    }

    if (lowlink[nod] == index[nod]) {
        nrcomp++;
        vector <int> componenta_curenta;
        do {
            top = st.top();
            st.pop();
            in_stack[top] = false;
            componenta_curenta.push_back(top);
        } while (top != nod);
        componente.push_back(componenta_curenta);
    }
}

void scrie() {
    int a, b;
    a = componente.size(); g << a << '\n';
    for (int i = 0; i < a; i++) {
        b = componente[i].size();
        for (int j = 0; j < b; j++) g << componente[i][j] << ' ';
        g << '\n';
    }
}


int main() {
    citeste();
    for (int i = 1; i <= n; i++)
        if (!index[i]) tarjan(i);
    scrie();
}