#include <bits/stdc++.h>
#define MAX 100100

using namespace std;

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

int n, m;
bool viz[MAX];
bool vizi[MAX];
int c[MAX], nrc;
vector <int> G[MAX];
vector <int> Gi[MAX];

void dostuff(){
    f >> n >> m;
    for (int i = 1; i <= m; ++i){
        int x, y;
        f    >> x >> y;
        G[x].push_back(y);
        Gi[y].push_back(x);
    }
}

void dfs(int node){
    viz[node] = true;
    for (int i = 0; i < G[node].size(); ++i){
        int newnode = G[node][i];
        if (!viz[newnode]){
            dfs(newnode);
        }
    }
}

void dfsi(int node){
    vizi[node] = true;
    for (int i = 0; i < Gi[node].size(); ++i){
        int newnode = Gi[node][i];
        if (!vizi[newnode]){
            dfsi(newnode);
        }
    }
}

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

void dothecheck(){
    for (int i = 1; i <= n; ++i){
        if ((viz[i] == true) && (vizi[i]) == true){
            c[i] = nrc;
        }
    }
}

void afish(){
    g << nrc << '\n';
    for (int i = 1; i <= nrc; i++){
        for (int j = 1; j <= n; j++){
            if (c[j] == i){
                g << j << ' ';
            }
        }
        g << '\n';
    }
}

void domorestuff(){
    for (int i = 1; i <= n; ++i){
        if (c[i] == 0){
            vizclear();
            nrc++;
            dfs(i);
            dfsi(i);
            dothecheck();
        }
    }
    afish();
}

int main()
{
    dostuff();
    domorestuff();
    return 0;
}