#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <cstring>
#define VMAX 100000

using namespace std;

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

int V, E, ctc;
bool vis[VMAX];
vector <int> adj[VMAX];
vector <int> trans[VMAX];
vector <int> comp[VMAX];
stack <int> st;

void DFS1(int u)
{
    vis[u] = true;
    for (auto w:adj[u])
        if (!vis[w]) DFS1(w);
    st.push(u);
}

void DFS2(int u)
{
    comp[ctc].push_back(u + 1);
    vis[u] = true;
    for (auto w:trans[u])
        if (!vis[w]) DFS2(w);
}
int main()
{
    fin >> V >> E;

    int x, y;

    while (E--) {
        fin >> x >> y;
        x--;
        y--;
        adj[x].push_back(y);
        trans[y].push_back(x);
    }

    for (int i = 0; i < V; ++i)
        if (!vis[i]) DFS1(i);

    memset(vis, 0, sizeof(vis));

    int u;
    while (!st.empty()) {
        u = st.top();
        if (!vis[u]) {
            DFS2(u);
            ctc++;
        }
        st.pop();
    }

    fout << ctc << '\n';

    for (int i = 0; i < ctc; ++i) {
        for (auto elem:comp[i]) fout << elem << " ";
        fout << '\n';
    }

    fin.close();
    fout.close();
    return 0;
}