#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <map>
using namespace std;

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

stack<int> parcurg;
int nrCtc;
vector<vector<int> > rez;
vector<int> comp, order;

void dfs(int rad, vector<vector<int> > adiacenta, vector<bool> &viz)
{
    viz[rad] = true;
    for(int nod : adiacenta[rad])
    {
        if(!viz[nod])
            dfs(nod, adiacenta, viz);
    }
    order.push_back(rad);
}

void dfs_t(int rad, vector<vector<int> > adiacenta_t, vector<bool> &viz)
{
    viz[rad] = true;
    comp.push_back(rad);
    for(int nod : adiacenta_t[rad])
    {
        if(!viz[nod])
            dfs_t(nod, adiacenta_t, viz);
    }
}

void kosaraju(int n, vector<vector<int> > adiacenta, vector<vector<int> > adiacenta_t)
{
    vector<bool> viz(n+1, false);
    for(int i=1; i<=n; i++)
    {
        if(!viz[i])
            dfs(i, adiacenta, viz);
    }

    fill(viz.begin(), viz.end(), false);
    for(int i=0; i<n; i++)
    {
        vector<int> sol;
        int nod = order[n-1-i];
        if(!viz[nod])
        {
            dfs_t(nod, adiacenta_t, viz);
            for(int j=0; j<comp.size(); j++)
                sol.push_back(comp[j]);
            rez.push_back(sol);
            sol.clear();
            comp.clear();
        }
    }
}

void print()
{
    out<<rez.size()<<endl;
    for(int i=0; i<rez.size(); i++)
    {
        for(int j=0; j<rez[i].size(); j++)
            out<<rez[i][j]<<" ";
        out<<endl;
    }
}

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

    vector<vector<int> > d(n+1, vector<int> (n+1, 0));
    vector<vector<int> > matrice(n+1, vector<int> (n+1, 0));
    vector<vector<int> > adiacenta (n+1);
    vector<vector<int> > adiacenta_t (n+1);
    vector<int> vcon (n+1, 0);
    vector<int> viz (n+1, 0);

    for(int i=1; i<=m; i++)
    {
        int x,y;
        in>>x>>y;
        matrice[x][y] = 1;
        adiacenta[x].push_back(y);
        adiacenta_t[y].push_back(x);
    }

    kosaraju(n, adiacenta, adiacenta_t);
    print();
    return 0;
}