#include <fstream>
#include <vector>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n,m,nrc;

vector<vector<int> > G,GT,CTC;
vector<bool> viz;
vector<int> Post;

void citire()
{
    int x,y;
    f>>n>>m;

    G = vector<vector<int> >(n+1);
    GT = vector<vector<int> >(n+1);
    CTC = vector<vector<int> >(n+1);
    viz = vector<bool>(n+1,0);
    Post = vector<int>(n+1);

    for(int i=1;i<=m;i++)
    {
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int vf)
{
    viz[vf] = 1;
    for(auto &x : G[vf])
        if(viz[x] == 0)
            dfs(x);
    Post.push_back(vf);
}

void dfsGT(int vf)
{
    viz[vf] = 0;
    CTC[nrc].push_back(vf);
    for(auto &x : GT[vf])
        if(viz[x] == 1)
            dfsGT(x);
}

void componente()
{
    for(int i=1;i<=n;i++)
        if(viz[i] == 0)
            dfs(i);

    for(auto it = Post.rbegin(); it != Post.rend(); ++it)
        if(viz[*it] == 1)
        { nrc++;
            dfsGT(*it);
        }
}

void afis()
{
    g<<nrc<<'\n';
    for(int i=1;i<=nrc;++i)
    {
        for(auto x:CTC[i])
            g<<x<<' ';
        g<<'\n';
    }
}

int main()
{
    citire();
    componente();
    afis();
    return 0;
}