#include <iostream>
#include <fstream>
#include <vector>
#include <string.h>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define MAX 100010
#define cout fout

vector<int> G[MAX], Gt[MAX], st;
vector<vector<int> > comp;
int viz[MAX];

void dfs(int nod, vector<int> G[], vector<int>& aux){
    viz[nod] = 1;
   // cout << G[nod].size();
    for(auto it : G[nod])
        if(!viz[it])
            dfs(it, G, aux);
    aux.push_back(nod);
}

void print(vector<int>& v){
    for(auto it:v){
        cout << it << " ";
    }
    cout << "\n";
}

int main(){
    int n, m, i, x, y;
    fin >> n >> m;
    while(m--){
        fin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(i = 1 ; i <= n ; i++){
        if(!viz[i]){
            dfs(i, G, st);
        }
    }
    memset(viz, 0, sizeof(viz));
    for(i = n - 1 ; i >= 0 ; i--){
        if(!viz[st[i]]){
            vector<int> aux;
            dfs(st[i], Gt, aux);
            comp.push_back(aux);
        }
    }
    cout << comp.size() << "\n";
    for(auto c : comp)
        print(c);

}