#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <bitset>
#define nmax 100101
#define pb push_back
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int k,n,m;
bitset<nmax> V;
vector <int> M[nmax];
vector <int> T[nmax];
vector <int> R[nmax];
vector <int> P;
void dfs(int nod){
    V[nod]=1;
    for(vector<int>::iterator it=M[nod].begin();it!=M[nod].end();++it){
        if(!V[*it]){
            dfs(*it);
        }
    }
    P.pb(nod);
}
void dfss(int nod){
    R[k].pb(nod);V[nod]=0;
    for(vector<int>::iterator it=T[nod].begin();it!=T[nod].end();++it){
        if(V[*it]){
            dfss(*it);
        }
    }
}
int main()
{
    f>>n>>m;int x,y;
    for(int i=1;i<=m;++i){
        f>>x>>y;
        M[x].pb(y);
        T[y].pb(x);
    }
    for(int i=1;i<=n;i++){
        if(!V[i]){
            dfs(i);
        }
    }k=0;
    reverse(P.begin(), P.end());
    for(vector<int>::iterator it=P.begin();it!=P.end();++it){
        if(V[*it]){
            ++k;
            dfss(*it);

        }
    }
    g<<k<<"\n";
    for(int i=1;i<=k;++i){
        for(vector<int>::iterator it=R[i].begin();it!=R[i].end();++it){
            g<<*it<<" ";
        }g<<"\n";
    }
    return 0;
}