#include <bits/stdc++.h>
using namespace std;
  
ifstream in("ctc.in");
ofstream out("ctc.out");

const int NMax = 1e5 + 5;

vector< vector< int > > G, GTranspose, componenteTareConexe(NMax);
vector< bool > viz;
stack< int > s;

void DFS(int nod) {
    viz[nod] = true;

    for(auto vecin: G[nod]) {
        if(!viz[vecin]) {
            DFS(vecin);
        }
    }
    s.push(nod);
}

void DFSTranspose(int nod, int nrComponenta) {
    viz[nod] = true;
    componenteTareConexe[nrComponenta].push_back(nod);

    for(auto vecin: GTranspose[nod]) {
        if(!viz[vecin]) {
            DFSTranspose(vecin, nrComponenta);
        }
    }
}

int main() {

    int n, m; in >> n >> m;

    G.resize(n + 1); GTranspose.resize(n + 1); viz.resize(n + 1);

    for(int i = 1; i <= m; ++i) {
        int x, y; in >> x >> y;
        G[x].push_back(y);
        GTranspose[y].push_back(x);
    }

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

    int nrComponente = 0;
    while(!s.empty()) {
        int tempNode = s.top(); s.pop();

        if(!viz[tempNode]) {
            nrComponente++;
            DFSTranspose(tempNode, nrComponente);
        }
    }

    out << nrComponente << '\n';
    for(int i = 1; i<= nrComponente; ++i) {
        for(auto componenta: componenteTareConexe[i]) {
            out << componenta << " ";
        }
        out << '\n';
    }

    in.close(); out.close();
  
    return 0;
}