#include <fstream>
#include <vector>
using namespace std;

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

int s;
int nr[100001];
bool ok[100001];
vector<vector<int> > sl;
vector<int> v[100001],rv[100001];

void dfs1(int i){
    for(unsigned j=0;j<v[i].size();j++)
        if(!ok[v[i][j]]){
            ok[v[i][j]]=1;
            dfs1(v[i][j]);
        }
    s++;
    nr[s]=i;
    return;
}

void dfs2(int i){
    for(unsigned j=0;j<rv[i].size();j++)
        if(ok[rv[i][j]]){
            ok[rv[i][j]]=0;
            dfs2(rv[i][j]);
        }
    sl.back().push_back(i);
    return;
}

int main()
{
    int n,m;
    f>>n>>m;

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

    for(int i=n;i>0;i--)
        if(!ok[i]){
            ok[i]=1;
            dfs1(i);
        }

    for(int i=n;i>0;i--)
        if(ok[nr[i]]){
            sl.push_back(vector<int> (0));
            ok[nr[i]]=0;
            dfs2(nr[i]);
        }

    g<<sl.size()<<'\n';

    for(unsigned i=0;i<sl.size();i++,g<<'\n')
        for(unsigned j=0;j<sl[i].size();g<<sl[i][j]<<" ",j++);

    return 0;
}