#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

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

const int maxn = 1e5 + 5;
vector <int> G[maxn], Gt[maxn], CTC[maxn];
bitset <maxn> Vis;
int V[maxn], CTC_size;

void Dfs_1 (int node) {
    vector <int> :: iterator it;
    Vis[node] = true;
    for (it = G[node].begin(); it != G[node].end(); it++) {
        if (Vis[*it] == false) {
            Dfs_1(*it);
        }
    }
    V[++V[0]] = node;
}

void Dfs_2 (int node) {
    vector <int> :: iterator it;
    Vis[node] = false;
    CTC[CTC_size].push_back(node);
    for (it = Gt[node].begin(); it != Gt[node].end(); it++) {
        if (Vis[*it] == true) {
            Dfs_2(*it);
        }
    }
}

int main() {
    ios_base :: sync_with_stdio (false);
    vector <int> :: iterator it;
    int n, m, x, y, i;
    fin >> n >> m;
    for (i = 1; i <= m; i++) {
        fin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for (i = 1; i <= n; i++) {
        if (Vis[i] == false) {
            Dfs_1(i);
        }
    }
    for (i = n; i > 0; i--) {
        if (Vis[V[i]] == true) {
            CTC_size++;
            Dfs_2(V[i]);
        }
    }
    fout << CTC_size << "\n";
    for (i = 1; i <= CTC_size; i++) {
        for (it = CTC[i].begin(); it != CTC[i].end(); it++) {
            fout << *it << " ";
        }
        fout << "\n";
    }
    fin.close();
    fout.close();
    return 0;
}