#include <fstream>
#include <vector>
#include <algorithm>
#define DIM 100002
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> v[DIM],sol[DIM];
int n,m,viz[DIM],s[DIM],k;
void DFST(int x){
    viz[x]=0;
    sol[k].push_back(x);
    for(int i=0;i<v[x].size();i++)
        if(viz[v[x][i]])
            DFST(v[x][i]);
}
void DFS(int x){
    viz[x]=1;
    for(int i=0;i<v[x].size();i++)
        if(!viz[v[x][i]])
            DFS(v[x][i]);
    s[++k]=x;
}
int main(){
    fin>>n>>m;
    while(m--){
        int x,y;
        fin>>x>>y;
        v[x].push_back(y);
    }
    for(int i=1;i<=n;i++)
        if(!viz[i])
            DFS(i);
    k=0;
    for(int i=1;i<=n;i++)
        if(viz[s[i]]){
            k++;
            DFST(s[i]);
        }
    fout<<k<<"\n";
    for(int i=k;i>=1;i--){
        sort(sol[i].begin(),sol[i].end());
        for(int j=0;j<sol[i].size();j++)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    fin.close();fout.close();
    return 0;
}