#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
#define N_MAX 100005
int n, m, viz[N_MAX], vizt[N_MAX], dim;
vector <int> G[N_MAX], GT[N_MAX], s, ctc[N_MAX];
void dfs(int nod)
{
    viz[nod] = 1;
    for(auto it: G[nod])
    {
        if(!viz[it])
            dfs(it);
    }
    s.push_back(nod);
}

void dfst(int nod)
{
    ctc[dim].push_back(nod);
    vizt[nod] = 1;
    for(auto it: GT[nod])
    {
        if(!vizt[it])
            dfst(it);
    }
}
int main()
{
    f >> n >> m;
    int x, y;
    for(int i = 1; i <= m; i++)
    {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!viz[i]) dfs(i);
    while(s.size())
    {
        int nod = s.back();
        s.pop_back();
        if(!vizt[nod])
        {
            dim++;
            dfst(nod);
        }
    }
    g << dim << "\n";
    for(int i = 1; i<= dim; i++)
    {
        for(auto it : ctc[i])
            g << it << " ";
        g << "\n";
    }
    return 0;
}