#include <bits/stdc++.h>
#define Nmax 100009

using namespace std;

#define USE_FILES 1

#ifdef USE_FILES
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define cin fin
#define cout fout
#endif // USE_FILES

int n,m,x,y,sol;
vector<int> G[Nmax],Gt[Nmax],sortaret;
vector <int> ctc[Nmax];
bitset <Nmax> viz;

void DFS1(int node) {

    viz[node]=1;

    for (auto x: G[node])
        if (!viz[x]) DFS1(x);

    sortaret.push_back(node);
}

void DFS2(int node) {

    viz[node]=0;
    ctc[sol].push_back(node);

    for (auto x: Gt[node])
        if (viz[x]) DFS2(x);


}

int main() {

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

        cin>>x>>y;

        G[x].push_back(y);
        Gt[y].push_back(x);
    }

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

        if (!viz[i]) {

            DFS1(i);
        }
    }

    reverse(sortaret.begin(), sortaret.end());

    for (auto x: sortaret)
        if (viz[x]) {

            ++sol;
            DFS2(x);

        }

    cout<<sol<<'\n';

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

        for (auto x: ctc[i]) cout<<x<<' ';
        cout<<'\n';
    }

    return 0;
}