#include <fstream>
#include <vector>
using namespace std;

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


int n, m, q;
int k, DUD[100006];
bool viz[100001];

vector <int> V1[100001];
vector <int> V2[100001];
vector <int> ctc[100001];



void DFS1(int nod){

    viz[nod] = 1;

    for(auto it : V1[nod])
        if(!viz[it])
            DFS1(it);

    DUD[++k] = nod;
}



void DFS2(int nod){

    viz[nod] = 0;
    ctc[q].push_back(nod);

    for(auto it : V2[nod])
        if(viz[it] == 1)
            DFS2(it);
}



int main(){

    fin >> n >> m;

    for(int i = 1; i <= m; i++){

        int x, y;
        fin >> x >> y;

        V1[x].push_back(y);
        V2[y].push_back(x);
    }

    for(int i = 1; i <= n; i++)
        if(!viz[i])
            DFS1(i);

    for(int i = n; i >= 1; i--)
        if(viz[DUD[i]] == 1){
                q++;
                DFS2(DUD[i]);
            }

    fout << q << '\n';

    for(int i = 1; i <= q; i++){

        for(auto it : ctc[i])
            fout << it << ' ';

        fout << '\n';
    }

    return 0;

}