#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int> A[100005],TA[100005],CTC[100005];
stack<int> S;

int N,M,cate_conexe;

int VIZ[100005],TVIZ[100005];

void df (int x)
{
    VIZ[x]=1;
    vector<int> :: iterator it;
    for (it=A[x].begin();it!=A[x].end();++it)
    {
        int val=(*it);
        if (VIZ[val]==0)
        {
            df(val);
        }
    }
    S.push(x);
}

void tdf (int x)
{
    TVIZ[x]=1;
    CTC[cate_conexe].push_back(x);
    vector<int> :: iterator it;
    for (it=TA[x].begin();it!=TA[x].end();++it)
    {
        int val=(*it);
        if (TVIZ[val]==0)
        {
            tdf(val);
        }
    }
}

int main()
{
    fin >> N >> M;
    int a,b,i;
    for (i=1;i<=M;++i)
    {
        fin >> a >> b;
        A[a].push_back(b);
        TA[b].push_back(a);
    }
    for (i=1;i<=N;++i)
    {
        if (VIZ[i]==0)
        {
            df(i);
        }
    }
    /*
    while (!S.empty())
    {
        cout << S.top() << '\n';
        S.pop();
    }
    */
    while (!S.empty())
    {
        i=S.top();
        S.pop();
        if (TVIZ[i]==0)
        {
            ++cate_conexe;
            tdf(i);
        }
    }
    fout << cate_conexe << '\n';
    for (i=1;i<=cate_conexe;++i)
    {
        vector<int> :: iterator it;
        for (it=CTC[i].begin();it!=CTC[i].end();++it)
        {
            int val=(*it);
            fout << val << " ";
        }
        fout << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}