#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
/*
8 12
1 2
2 6
6 7
7 6
3 1
3 4
2 3
4 5
5 4
6 5
5 8
8 7
*/
int n, m, nr;
vector <vector <int> > a;
vector <vector <int> > arev;
vector <vector <int> > afis;
vector <bool> viz;
stack <int> st;
void df(int k) {
    viz[k] = true;
    for (int i = 0 ; i < a[k].size(); i++) {
        if (viz[a[k][i]] == false) {
            df(a[k][i]);
        }
    }
    st.push(k);
}
void dfrev(int k) {
    viz[k] = true;
    afis[nr].push_back(k);
    for (int i = 0 ; i < arev[k].size(); i++) {
        if (viz[arev[k][i]] == false) {
            dfrev(arev[k][i]);
        }
    }
}
int main()
{
    fin>>n>>m;
    a.resize(n + 1);
    arev.resize(n + 1);
    viz.resize(n + 1);
    int x, y;
    for (int i = 1; i <= m; i++) {
        fin>>x>>y;
        a[x].push_back(y);
        arev[y].push_back(x);
    }

    for (int i = 1; i <= n; i++) {
        if (viz[i] == false) {
            df(i);
        }
    }

    for(int i = 0; i < viz.size(); i++) {
        viz[i] = false;
    }
    while(!st.empty()) {
        int k = st.top();
        st.pop();
        if(viz[k] == false) {
            nr++;
            afis.resize(nr + 1);
            dfrev(k);
        }
    }
    fout<<nr;
    fout<<'\n';
    for (int i = 1; i < afis.size(); i++) {
        for (int j = 0; j < afis[i].size(); j++) {
            fout<<afis[i][j]<<' ';
        }
        fout<<'\n';
    }
    /*
    cout<<st.size();
    while(!st.empty()) {
        cout<<st.top()<<' ';
        st.pop();
    }
    */

    fin.close();
    fout.close();
    return 0;
}
/*
#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m;
vector <vector <int> > a;
vector <int> st;
vector <bool> viz;
void df(int k) {
    viz[k] = true;
    for (int i = 0 ; i < a[k].size(); i++) {
        if (viz[a[k][i]] == false) {
            viz[a[k][i]] = true;
            df(a[k][i]);
        }
    }
    st.push_back(k);
}
int main()
{
    fin>>n>>m;
    a.resize(n + 1);
    viz.resize(n + 1);
    int x, y;
    for (int i = 1; i <= m; i++) {
        fin>>x>>y;
        a[x].push_back(y);
    }
    df(2);
    for(int i = 0; i < st.size(); i++) {
        fout<<st[i]<<' ';
    }
    fin.close();
    fout.close();
    return 0;
}
*/