#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include <string>
#include <cstring>
#define ll long long

using namespace std;

void top_sort(int node, vector<bool> &vis, vector<vector<int>> &g, vector<int> &sorted) {
    vis[node] = 1;
    for(auto it : g[node])
        if(!vis[it])
            top_sort(it, vis, g, sorted);
    sorted.push_back(node);
}

int dfs(int node, vector<bool> &vis, vector<vector<int>> &g, vector<int> &component) {
    vis[node] = 1;
    component.push_back(node);
    for(auto it : g[node])
        if(!vis[it])
            dfs(it, vis, g, component);
}

int main() {
    ifstream in("ctc.in");
    ofstream out("ctc.out");

    int n, m;
    in >> n >> m;
    vector<vector<int>> g(n + 1);
    vector<vector<int>> gT(n + 1);
    for(int i = 1; i <= m; i ++) {
        int x, y;
        in >> x >> y;
        g[x].push_back(y);
        gT[y].push_back(x);
    }

    vector<bool> vis(n + 1, 0);
    vector<int> top_sorted;
    for(int i = 1; i <= n; i ++)
        if(!vis[i])
            top_sort(i, vis, g, top_sorted);
    reverse(top_sorted.begin(), top_sorted.end());

    for(int i = 1; i <= n; i ++)
        vis[i] = 0;
    vector<vector<int>> ans;
    vector<int> aux;
    for(auto i : top_sorted) {
        if(!vis[i]) {
            aux.clear();
            dfs(i, vis, gT, aux);
            reverse(aux.begin(), aux.end());
            ans.push_back(aux);
        }
    }
    out << ans.size() << "\n";
    for(auto it : ans) {
        for(auto it2 : it)
            out << it2 << " ";
        out << "\n";
    }

    return 0;
}