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

const int nmax = 100006;
int n, m, st[nmax], nrcomp, lst;
vector < int > vecini[nmax], antivec[nmax], v[nmax];
bool poz[nmax];
 
void top_sort(int nod)
{
    poz[nod] = 1;
 
    for(int i = 0; i<vecini[nod].size(); i++)
        if(!poz[vecini[nod][i]])
			top_sort(vecini[nod][i]);
 
    st[++lst] = nod;
}
 
void dfs(int nod)
{
    poz[nod] = 0;
    v[nrcomp].push_back(nod);
 
    for(int i = 0; i<antivec[nod].size(); i++)
        if(poz[antivec[nod][i]])
			dfs(antivec[nod][i]);
}
int main()
{
    int player_unu=0;

    in>>n>>m;
    for(int i = 1; i<=m; i++)
    {
		int x,y;
        in>>x>>y;

        vecini[x].push_back(y);
        antivec[y].push_back(x);
    }
 
    for(int i = 1; i<=n; i++)
        if(!poz[i]) 
			top_sort(i);
 
    for(int i = n; i>0; i--)
    {
        if(poz[st[i]])
        {
            ++nrcomp;
            dfs(st[i]);
        }
    }
 
    out<<nrcomp<<'\n';
    for(int i = 1; i<=nrcomp; i++)
    {
        for(int j = 0; j<v[i].size(); j++)
            out<<v[i][j]<<' ';
 
      out<<'\n';
	}

    return player_unu;
}