#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], top, ans;

void Dfs1 (int node) {
    vector <int> :: iterator it;
    Vis[node] = true;
    for (it = G[node].begin(); it != G[node].end(); it++) {
        if (Vis[*it] == false) Dfs1(*it);
    }
    V[++top] = node;
}

void Dfs2(int node) {
    vector <int> :: iterator it;
    Vis[node] = false;
    Ctc[ans].push_back(node);
    for (it = Gt[node].begin(); it != Gt[node].end(); it++) {
        if (Vis[*it] == true) Dfs2(*it);
    }
}

int main() {
    ios_base :: sync_with_stdio (false);
    int n, m, x, y, i, j;
    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) {
            Dfs1(i);
        }
    }
    for (i = n; i > 0; i--) {
        if (Vis[V[i]] == true) {
            ans++;
            Dfs2(V[i]);
        }
    }
    fout << ans << "\n";
    for (i = 1; i <= ans; i++) {
        for (j = 0; j < (int)Ctc[i].size(); j++) {
            fout << Ctc[i][j] << " ";
        }
        fout << "\n";
    }
    fin.close();
    fout.close();
    return 0;
}