#include<fstream>
#include<iostream>
#include<vector>
#include<stack>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n,i,m,a,b,j,nr;

vector<int>v[100001],vt[100001];

bool viz[100001],Viz[100001];

vector<int>compcon[100001];
stack<int>st;

void citire(){

    f >> n>>m;

    for(int i = 1; i <= m; i++){

        f>> a >> b;

        v[a].push_back(b);
        vt[b].push_back(a);
    }

}


void dfs(int vf){

    viz[vf]=true;

    for(int i=0; i<v[vf].size(); i++)

        if(!viz[v[vf][i]])
            dfs(v[vf][i]);



    st.push(vf);

}

void Dfs(int vf){

    Viz[vf]=true;

    for(int i=0; i<vt[vf].size(); i++)

        if(!Viz[vt[vf][i]]){

            Dfs(vt[vf][i]);

            compcon[j].push_back(vt[vf][i]);
        }

}




int main(){

    citire();

    for(j=1; j<=n; j++){

        if(!viz[j])

            dfs(j);

    }

    while(!st.empty()){

        j=st.top();

        st.pop();

        if(!Viz[j]){

            Dfs(j);

            nr++;

            compcon[j].push_back(j);

        }

    }

    g<<nr<<"\n";

    for(i=1; i<=n; i++){

        if(compcon[i].size()){

            for(j=0; j<compcon[i].size(); j++)

                g<<compcon[i][j]<<" ";

            g<<"\n";

        }

    }

}