#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> graf[100001];
vector<int> transp[100001];
vector<int> ctc[100001];
int sortT[100001];
bool viz[100001];
int nc;
int pozT;

void dfsSortT (int nod) {
    viz[nod] = true;
    vector<int>::iterator it;
    for (it = graf[nod].begin(); it != graf[nod].end(); it++) {
        if (!viz[*it]) {
            dfsSortT(*it);
        }
    }
    sortT[pozT++] = nod;
}

void dfsTransp (int nod) {
    viz[nod] = true;
    ctc[nc].push_back(nod);
    vector<int>::iterator it;
    for (it = transp[nod].begin(); it != transp[nod].end(); it++) {
        if (!viz[*it]) {
            dfsTransp(*it);
        }
    }
}

void reinit (int n) {
    for (int i = 1; i <= n; i++)
        viz[i] = false;
}

int main() {
    ifstream file_in ("ctc.in");
    ofstream file_out ("ctc.out");

    int n, m;
    int u, v;
    int i;

    file_in >> n >> m;
    for (i = 0; i < m; i++) {
        file_in >> u >> v;
        graf[u].push_back(v);
        transp[v].push_back(u);
    }

    for (i = 1; i <= n; i++) {
        if (!viz[i]) {
            dfsSortT(i);
        }
    }

    reinit(n);
    for (i = n - 1; i >= 0; i--) {
        if (!viz[sortT[i]]) {
            nc++;
            dfsTransp(sortT[i]);
        }
    }

    file_out << nc << "\n";
    vector<int>::iterator it;
    for (i = 1; i <= nc; i++) {
        sort(ctc[i].begin(), ctc[i].end());
        for (it = ctc[i].begin(); it != ctc[i].end(); it++) {
            file_out << *it << " ";
        }
        file_out << "\n";
    }

    return 0;
}