#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
ifstream f ("ctc.in") ;
ofstream g ("ctc.out") ;
int N, M ,  K , x , y,  i , Sol = 0;
vector <int> G[NMAX] , GT[NMAX] , sol[NMAX];
stack <int> st;
bool viz[NMAX] ;
void DFS (int nod)
{
    viz[nod] = true;
    int len = G[nod].size();
    for (int i = 0 ; i < len ; ++i)
        if (!viz[G[nod][i]]) DFS(G[nod][i]);

    st.push(nod);
}
void DFST (int nod)
{
    viz[nod] = false;
    int len = GT[nod].size();
    for (int i = 0 ; i < len ; ++i)
        if (viz[GT[nod][i]]) DFST(GT[nod][i]);
    sol[Sol].push_back(nod);
}
int main()
{
    f >> N >> M;
    for (int i = 1 ; i <= M; ++i)
    {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for (int nod = 1 ; nod <= N ; ++nod)
        if (!viz[nod])  DFS(nod);

    while (!st.empty())
    {
        int nod = st.top();
        st.pop();
        if (viz[nod])
        {
             Sol ++ ;
            DFST(nod);
        }
    }
    g << Sol << '\n';
    for (int i = 1 ; i <= Sol ; ++i)
    {
        int len = sol[i].size();
        for (int j = 0 ; j < len; ++j) g << sol[i][j]<< ' ';
        g << '\n';
    }
    f.close();
    g.close();
    return 0;
}