#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
#define MAX 100005

using namespace std;

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

vector <int> G[MAX], GT[MAX], C[MAX];
int stiva[MAX], varf, comp_con;
bitset <MAX> viz, vizt;

void dfs(int nod)
{
    viz[nod] = 1;
    for(int i = 0; i < G[nod].size(); i++)
        if(viz[G[nod][i]] == 0)
            dfs(G[nod][i]);
    stiva[++varf] = nod;
}

void dfss(int nod)
{
    vizt[nod] = 1;
    for(int i = 0; i < GT[nod].size(); i++)
        if(vizt[GT[nod][i]] == 0)
            dfss(GT[nod][i]);
}

int main()
{
    int N, M, i, x, y;
    f>>N>>M;
    for(i = 1; i <= M; i++)
    {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(i = 1; i <= N; i++)
        if(viz[i] == 0)
            dfs(i);
    while(varf!= 0)
    {
        int nod = stiva[varf];
        dfss(nod);
        comp_con++;
        for(int j = 1; j <= varf; j++)
            if(vizt[stiva[j]] == 1)
                {
                    C[comp_con].push_back(stiva[j]);
                    for(int k = j; k <varf; k++)
                        stiva[k] = stiva[k+1];
                    j--;
                    varf--;
                }
    }
    g<<comp_con<<'\n';
    for(i = 1; i <= comp_con; i++)
    {
        for(int j = 0; j < C[i].size(); j++)
            g<<C[i][j]<<" ";
        g<<'\n';
    }
    return 0;
}