#include <bits/stdc++.h>


using namespace std;
vector<int>S,G[100001],GT[100001];
int f[100001],f2[100001],cnt=0,n,m;
set<int>lista[100001];
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int comp[100001],f3[100001];
void dfs(int nod){
    f[nod]=1;
    for(auto x : G[nod])
        if(!f[x])
            dfs(x);
    S.push_back(nod);
}
void dfs2(int nod){
    f2[nod]=1;
    lista[cnt].insert(nod);
    comp[nod]=cnt;
    for(auto x : GT[nod])
        if(!f2[x])
            dfs2(x);
}
int main(){
    fin>>n>>m;
    while(m--){
        int x,y; fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!f[i])
            dfs(i);
    for(vector<int> :: reverse_iterator it= S.rbegin(); it!=S.rend();it++)
    if(!f2[*it]){
        cnt++;
        dfs2(*it);
    }
    fout<<cnt<<'\n';
    for(int i=1;i<=n;i++)
        if(!f3[comp[i]]){
            /// componenta lui i nu a fost afisata
            f3[comp[i]]=1;
            for(auto x : lista[comp[i]])
                fout<<x<<" ";
            fout<<'\n';
        }
    return 0;
}