#include <fstream>
#include <vector>
#include <algorithm>
#define dim 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,i,j,a,b,viz[dim],k,s[dim],m;
vector<int> v[dim],sol[dim],f[dim];
void DFS(int nod){
    viz[nod]=0;
    sol[k].push_back(nod);
    for(int i=0;i<f[nod].size();i++){
        if(viz[f[nod][i]]==1){
            DFS(f[nod][i]);
        }
    }
}
void dfs(int nod){
    viz[nod]=1;
    for(int i=0;i<v[nod].size();i++){
        if(viz[v[nod][i]]==0){
            dfs(v[nod][i]);
        }
    }
    s[++k]=nod;

}
int main(){
    fin>>n>>m;
    for(i=1;i<=m;i++){
        fin>>a>>b;
        v[a].push_back(b);
        f[b].push_back(a);
    }
    for(i=1;i<=n;i++){
        if(viz[i]==0){
            dfs(i);
        }
    }
    k=0;
    for(i=n;i>=1;i--){
        if(viz[s[i]]){
            k++;
            DFS(s[i]);
        }

    }
    fout<<k<<"\n";
    for(i=1;i<=k;i++){
        sort(sol[i].begin(),sol[i].end());
        for(j=0;j<sol[i].size();j++){
            fout<<sol[i][j]<<" ";
        }
        fout<<"\n";
    }

    return 0;
}