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

using namespace std;

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

int n, m, scc, visited[100001];
vector <int> G[100001], GT[100001], SCC[100001];
stack <int> S;

void Read()
{
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void Print()
{
    g << scc << endl;
    for (int i = 1; i <= scc; i++)
    {
        for (int j = 0; j < SCC[i].size(); j++)
        {
            g << SCC[i][j] << " ";
        }
        g << endl;
    }
}

void DFS1(int at)
{
    visited[at] = 1;
    for (int i = 0; i < G[at].size(); i++)
    {
        int to = G[at][i];
        if (visited[to] == 0)
        {
            DFS1(to);
        }
    }
    S.push(at);
}

void DFS2(int at)
{
    visited[at] = 2;
    SCC[scc].push_back(at);

    for (int i = 0; i < GT[at].size(); i++)
    {
        int to = GT[at][i];
        if (visited[to] == 1)
        {
            DFS2(to);
        }
    }
}

void Solve()
{
    for (int i = 1; i <= n; i++)
    {
        if (visited[i] == 0)
        {
            DFS1(i);
        }
    }

    while (S.empty() == false)
    {
        int node = S.top();
        if (visited[node] == 1)
        {
            scc++;
            DFS2(node);
        }
        S.pop();
    }
}

int main()
{
    Read();
    Solve();
    Print();
}