#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <deque>

using namespace std;

const char infile[] = "ctc.in";
const char outfile[] = "ctc.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 100005;
const int oo = 0x3f3f3f3f;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

class DirectedGraph {
private:
    vector <vector <int> > adj;
    vector <bool> used;
    int N;
public:
    DirectedGraph() {
    }
    DirectedGraph(int _N) {
        adj.resize(_N);
        used.resize(_N, 0);
        N = _N;
    }
    void addDirectedEdge(int x, int y) {
        adj[x].push_back(y);
    }
    void dfs(int node, vector <int> &v) {
        if(used[node])
            return;
        used[node] = 1;
        for(auto it:adj[node])
            if(!used[it])
                dfs(it, v);
        v.push_back(node);
    }
    void getTsort(int node, vector <int> &v) {
        if(used[node])
            return;
        used[node] = 1;
        for(auto it:adj[node])
            if(!used[it])
                getTsort(it, v);
        v.push_back(node);
    }
};

int main() {
    cin.sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
    freopen(infile, "r", stdin);
    freopen(outfile, "w", stdout);
    #endif
    int N, M;
    fin >> N >> M;
    DirectedGraph G(N), Gt(N);
    for(; M -- ;) {
        int x, y;
        fin >> x >> y;
        --x ; -- y;
        G.addDirectedEdge(x, y);
        Gt.addDirectedEdge(y, x);
    }
    vector <int> tsort;
    vector <vector <int> > CTC;
    for(int i = 0 ; i < N ; ++ i)
        G.getTsort(i, tsort);
    for(auto it = tsort.rbegin() ; it != tsort.rend(); ++ it) {
        vector <int> act;
        Gt.dfs(*it, act);
        if(!act.empty())
            CTC.push_back(act);
    }
    fout << CTC.size() << '\n';
    for(auto it : CTC) {
        for(auto el: it)
            fout << el + 1 << ' ';
        fout << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}