#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;

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

vector <int> Gi[100005];
vector <int> Go[100005];
int n, m;
bool visited[100005];
vector<int> discovered;
int where[100005];
int comp;

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

void dfs(int x) {
    visited[x] = true;
    for(int i = 0; i < Go[x].size(); i++) {
        int y = Go[x][i];
        if(!visited[y])
            dfs(y);
    }
    discovered.push_back(x);
}

void Assign(int x, int root) {
    where[x] = root;
    for(int i = 0; i < Gi[x].size(); i++) {
        int y = Gi[x][i];
        if(where[y] == -1)
            Assign(y, root);
    }
}

void afis() {
    g << comp << '\n';
    for(int nr = 0; nr < comp; nr++) {
        for(int i = 1; i <= n; i++)
            if(where[i] == nr)
                g << i << ' ';
        g << '\n';
    }
}

int main() {
    citire();
    for(int i = 1; i <= n; i++)
        if(!visited[i])
            dfs(i);

    memset(where, -1, sizeof where);

    for( ;discovered.size(); discovered.pop_back()) {
        int b = discovered[discovered.size()-1];
        if(where[b] == -1) {
            Assign(b, comp);
            comp++;
        }
    }

    afis();
}