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

using namespace std;

const int N = 1e5 + 1;

vector <int> L[N], T[N];
vector <vector <int> > ctc;
bitset <N> vis;
int n, nr_ctc = -1;
stack<int> st;

void Read()
{
    ifstream fin ("ctc.in");
    int m;
    fin >> n >> m;
    while (m--)
    {
        int x, y;
        fin >> x >> y;
        L[x].push_back(y);
        T[y].push_back(x);
    }
    fin.close();
}

void First_DFS(int node)
{
    vis[node] = 1;
    for (auto& next : L[node])
        if (!vis[next])
            First_DFS(next);
    st.push(node);
}

void Second_DFS(int node)
{
    vis[node] = 1;
    ctc[nr_ctc].push_back(node);
    for (auto& next : T[node])
        if (!vis[next])
            Second_DFS(next);
}

void Kosaraju() {
    for (int i = 1; i <= n; i++)
        if (!vis[i])
            First_DFS(i);
    vis.reset();
    while (!st.empty())
    {
        int curr = st.top();
        st.pop();
        if (!vis[curr])
        {
            nr_ctc++;
            ctc.push_back({});
            Second_DFS(curr);
        }
    }
    ofstream fout ("ctc.out");
    fout << ctc.size() << "\n";
    for (int i = 0; i < ctc.size(); i++, fout << "\n")
        for (int j = 0; j < ctc[i].size(); j++)
            fout << ctc[i][j] << " ";
    fout.close();
}

int main() {
    Read();
    Kosaraju();
    return 0;
}