#include <fstream>
#include <vector>
#define NMAX 100001

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

bool uz[NMAX];
int n, m, nr, nrc;  /// nrc = numarul de componente tare conexe
int postordine[NMAX], ctc[NMAX]; /// ctc[i] = componenta tare conexa din care face parte vf i
vector<int> G[NMAX];
vector<int> GT[NMAX];

void read();
void DFS(int k);
void DFST(int k);
void print();

int main(){int i;
    read();
    for(i = 1; i <= n; i++)
        if(!uz[i]) DFS(i);
    print();
    return 0;
}

void read(){int i, x , y;
    fin >> n >> m;
    for(i = 0; i< m; i++){
        fin >> x >> y;
        G[x].push_back(y);
        /// in graful transpus pun arcul invers
        GT[y].push_back(x);
    }
}

void DFS(int k){unsigned int i;
    uz[k] = 1;
    for(i = 0; i < G[k].size(); i++)
        if(!uz[G[k][i]]) DFS(G[k][i]);
    nr++;
    postordine[nr] = k;
}

void print(){int i, j;
    for(i = n; i > 0; i--)
        if(!ctc[postordine[i]]){
            nrc++;
            DFST(postordine[i]);
        }
    fout << nrc << '\n';
    for(i = 1; i <= nrc; i++){
        for(j = 1; j <= n; j++)
            if(ctc[j] == i) fout << j << ' ';
        fout << '\n';
    }

}

void DFST(int k){unsigned int i;
    ctc[k] = nrc;
    for(i = 0; i < GT[k].size(); i++)
        if(!ctc[GT[k][i]]) DFST(GT[k][i]);
}