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

#define MAXN 100001

using namespace std;
using Graph = vector<vector<int> >;

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

Graph G(MAXN), Gt(MAXN), stronglyCtc(MAXN);
int N, M, currTime, currentCtc;
vector<int> visited(MAXN, 0), order(MAXN, 0);

void dfs(int source)
{
    visited[source] = 1;
    for (auto &node : G[source])
        if (!visited[node])
            dfs(node);
    order[++currTime] = source;
}

void dfsT(int source)
{
    visited[source] = 0;
    stronglyCtc[currentCtc].push_back(source);
    for (auto &node : Gt[source])
        if (visited[node])
            dfsT(node);
}

int main()
{
    in >> N >> M;

    int x, y;
    for (int i = 1; i <= M; i++) {
        in >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }

    for (int i = 1; i <= N; i++)
        if (!visited[i])
            dfs(i);

    for (int i = N; i >= 1; i--)
        if (visited[order[i]]) {
            ++currentCtc;
            dfsT(order[i]);
        }

    out << currentCtc << '\n';
    for (int i = 1; i <= currentCtc; i++) {
        for (auto &node : stronglyCtc[i])
            out << node << " ";
        out << '\n';
    }

    return 0;
}