#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
int n, m, x, y, time, nr;
vector<int> L[100002], L2[100002], v, comp[100002];
bool viz[100002], viz2[100002];
void dfs(int nod){
    //time++;
    viz[nod]=1;
    for(int i=0;i<L[nod].size();i++){
        int vecin=L[nod][i];
        if(!viz[vecin]){
            dfs(vecin);
        }
    }
    //time++;
    v.push_back(nod);
}
void dfs2(int nod){
    viz2[nod]=1;
    comp[nr].push_back(nod);
    for(int i=0;i<L2[nod].size();i++){
        int vecin=L2[nod][i];
        if(!viz2[vecin]){
            dfs2(vecin);
        }
    }
}
int main() {
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>x>>y;
        L[x].push_back(y);
        L2[y].push_back(x);
    }
    for(int i=1;i<=n;i++){
        if(!viz[i])
            dfs(i);
    }
    reverse(v.begin(), v.end());
    //time=0;
    for(int i=0;i<n;i++){
        if(!viz2[v[i]]){
            nr++;
            dfs2(v[i]);
        }
    }
    cout<<nr<<"\n";
    for(int i=1;i<=nr;i++){
        for(int j=0;j<comp[i].size();j++)
            cout<<comp[i][j]<<" ";
        cout<<"\n";
    }
}