#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

const int NMAX = 100001;

vector <int> s_top;
vector <int> s[NMAX];
vector <int> p[NMAX];
vector <int> ctc[NMAX];
bool viz[NMAX];

void resetare(int n){
    for(int i = 0; i <= n; i++){
        viz[i] = false;
    }
}

void dfs_1(int x){
    viz[x] = true;
    for(auto y: s[x]){
        if(!viz[y]){
            dfs_1(y);
        }
    }
    s_top.push_back(x);
}

void dfs_2(int x, int nr_c){
    viz[x] = true;
    ctc[nr_c].push_back(x);
    for(auto y: p[x]){
        if(!viz[y]){
            dfs_2(y, nr_c);
        }
    }
}

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

    int n, m;
    fin >> n >> m;

    for(int i = 0; i < m; i++){
        int x, y;
        fin >> x >> y;
        s[x].push_back(y);
        p[y].push_back(x);
    }

    for(int i = 1; i <= n; i++){
        if(!viz[i]){
            dfs_1(i);
        }
    }
    reverse(s_top.begin(), s_top.end());
    resetare(n);

    int nr_c = 1;
    for(auto x: s_top){
        if(!viz[x]){
            dfs_2(x, nr_c);
            nr_c++;
        }
    }

    fout << nr_c - 1 << "\n";

    for(int i = 1; i < nr_c; i++){
        for(auto x: ctc[i]){
            fout << x << " ";
        }
        fout << "\n";
    }

    fin.close();
    fout.close();
    return 0;
}