//Deresu Roberto - FMI
//Re :)
#include<fstream>
#include<vector>
#include<deque>
#define nx 100007
using namespace std;
int n, m, k, l, viz[nx], ord[nx];
vector<int> v[nx], t[nx], sol[nx];
deque<int> d, q;

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

void Dfs(int x)
{
    viz[x] = 1;
    sol[k].push_back(x);

    for (vector<int>::iterator it = t[x].begin(); it != t[x].end(); it++)
        if(viz[*it] == 0) Dfs(*it);
}

void Dfs1(int x)
{
    viz[x] = 1;

    for (vector<int>::iterator it = v[x].begin(); it != v[x].end(); it++)
        if(viz[*it] == 0) Dfs1(*it);

    k++;
    ord[k] = x;
}

void Re()
{
    for(int i = 1; i <= n; i++)
        if(viz[i] == 0) Dfs1(i);

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

    k = 0;
    for(int i = n; i >= 1; i--)
    {
        if(viz[ord[i]] == 0)
        {
            k++;
            Dfs(ord[i]);
        }
    }
}

void Read()
{
    fin >> n >> m;

    for(int i = 1; i <= m; i++)
    {
        int x, y;

        fin >> x >> y;
        v[x].push_back(y);
        t[y].push_back(x);
    }
}

void Print()
{
    fout << k << '\n';

    for(int i = 1; i <= k; i++)
    {
        for(vector<int>::iterator it = sol[i].begin(); it != sol[i].end(); it++)
        {
          fout << *it << " ";
        }

        fout << '\n';
    }
}

int main()
{
    Read();
    Re();
    Print();

    return 0;
}