#include <bits/stdc++.h>

using namespace std;

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

int n, m, nrctc;
vector<int> g[100005], gt[100005], tout, ctc[100005];
bitset<100005> used;

void dfs1(int node) {
    used[node] = true;
    for(auto elem : g[node]) {
        if(!used[elem]) {
            dfs1(elem);
        }
    }
    tout.push_back(node);
}

void dfs2(int node) {
    // out << nrctc << ' ' << node << '\n';
    used[node] = true;
    ctc[nrctc].push_back(node);
    for(auto elem : gt[node]) {
        if(!used[elem]) {
            dfs2(elem);
        }
    }
}

int main() {
    in >> n >> m;
    for(int i = 1; i <= m; i++) {
        int u, v; in >> u >> v;
        g[u].push_back(v);
        gt[v].push_back(u);
    }
    used = 0;
    for(int i = 1; i <= n; i++) {
        if(!used[i]) {
            dfs1(i);
        }
    }
    reverse(tout.begin(), tout.end());
    /*
    for(auto elem : tout) {
        out << elem << ' ';
    }
    out << '\n';
    */
    used = 0;
    for(auto elem : tout) {
        if(!used[elem]) {
            nrctc++;
            dfs2(elem);
        }
    }
    out << nrctc << '\n';
    for(int i = 1; i <= nrctc; i++) {
        sort(ctc[i].begin(), ctc[i].end());
        for(auto elem : ctc[i]) {
            out << elem << ' ';
        }
        out << '\n';
    }
    return 0;
}