#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include <string>
#include <cstring>
#include <set>
#include <queue>
#include <map>
#include <deque>
#define ll long long
#define lsb(x) (x & -x)

using namespace std;

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

const int NMAX = 100005;
vector<int> g[NMAX];
vector<int> gT[NMAX];

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

void dfs(int node, vector<bool> &visited, vector<int> &comp) {
    visited[node] = 1;
    comp.push_back(node);
    for(auto it : gT[node])
        if(!visited[it])
            dfs(it, visited, comp);
}

int main() {

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

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

    vector<bool> visitedT(n + 1, 0);
    vector<vector<int>> components;
    for(auto i : sorted) {
        if(!visitedT[i]) {
            vector<int> aux;
            dfs(i, visitedT, aux);
            components.push_back(aux);
        }
    }

    out << components.size() << "\n";
    for(auto &it : components) {
        for(auto &it2 : it)
            out << it2 << " ";
        out << "\n";
    }

    return 0;
}