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

using namespace std;

#define MAX_DIM 50005

std::vector <int> L[MAX_DIM];
std::vector <int> Lt[MAX_DIM];
std::vector <int> T;
int color[MAX_DIM];

std::vector <int> componente[MAX_DIM];
int nr_c = 0;

ifstream inFile("sortaret.in");
ofstream outFile("ctc.out");

void explor(int node)
{
    color[node] = 1;
    for(unsigned int i = 0; i < L[node].size(); i++) {
        int k = L[node][i];
        if( color[k] == 0 ) explor(k);
    }
    T.push_back(node);

}

void explor1(int node)
{
    componente[nr_c].push_back(node);
    color[node] = 1;
    for(unsigned int i = 0; i < Lt[node].size(); i++) {
        int k = Lt[node][i];
        if( color[k] == 0 ) explor1(k);
    }
}

int main()
{
    int n, m;
    inFile >> n >> m;

    int x, y;
    for(int i = 1; i <= m; i++) {
        inFile >> x >> y;
        L[x].push_back(y);
        Lt[y].push_back(x);
    }

    for(int node = 1; node <= n; node++) {
        if( color[node] == 0 ) explor(node);
    }

    for(unsigned int i = 0; i <= (T.size() - 1)/2; i++) {
        swap(T[i], T[T.size() - 1 - i]);
    }

    for(int i = 1; i <= n; i++) color[i] = 0;

    for(int i = 0; i < T.size(); i++) {
        int k = T[i];
        if(color[k] == 0) {explor1(k);  nr_c++; }
    }

    outFile << nr_c << "\n";
    for(int i = 0; i < nr_c; i++) {
        for(int j = 0; j < componente[i].size(); j++)
            outFile << componente[i][j] << " ";
        outFile << "\n";
    }
}