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

using namespace std;

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

struct compcon {
    vector<int> noduri;
} c[100005];

stack<int> S;

vector<int> G[100005];
vector<int> Gt[100005];

int n, m, viz[100005];
int nrc;

void citire() {
    fin>>n>>m;
    int x, y;
    for (int i=0; i<m; i++) {
        fin>>x>>y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
}

void dfs(int k) {
    viz[k]=1;
    for (auto i: G[k])
        if (!viz[i])
            dfs(i);
    S.push(k);
}

void dfs_gt(int k, int nr) {
    viz[k]=2;
    c[nrc].noduri.push_back(k);
    for (auto i: Gt[k])
        if (viz[i]==1)
            dfs_gt(i, nr);
}

void parcurgere1() {
    for (int i=1; i<=n; i++)
        if (!viz[i])
            dfs(i);
}

void parcurgere2() {
    while (!S.empty()) {
        if (viz[S.top()]==2) {
            S.pop();
            continue;
        }
        dfs_gt(S.top(), nrc);
        nrc++;
    }
}

void afisare() {
    fout<<nrc<<"\n";
    for (int i=0; i<nrc; i++) {
        for (auto j: c[i].noduri)
            fout<<j<<" ";
        fout<<"\n";
    }
}

int main() {
    citire();
    parcurgere1();
    parcurgere2();
    afisare();
    return 0;
}