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

#define DN 100005
#define pb push_back
using namespace std;


vector<int> list[DN],tmp,tr[DN];
vector< vector<int> > rez;
bitset<DN> viz;
int stiva[DN];

void dfs(int nod)
{
    viz[nod]=true;
    for(int i=0;i<list[nod].size();++i){

        int next_nod=list[nod][i];
        if(!viz[next_nod])
            dfs(next_nod);
    }
    stiva[++stiva[0]]=nod;
}

void dfs2(int nod)
{
    viz[nod]=true;
    tmp.push_back(nod);
    for(int i=0;i<tr[nod].size();++i){

        int next_nod=tr[nod][i];
        if(!viz[next_nod])
            dfs2(next_nod);
    }
}


int main()
{
    int n,m;
    ifstream f("ctc.in");
    ofstream g("ctc.out");
    f>>n>>m;
    for(;m;--m)
    {
        int a,b;
        f>>a>>b;
        list[a].pb(b);
        tr[b].pb(a);
    }

    for(int i=1;i<=n;++i)
        if(!viz[i])
            dfs(i);

    viz&=0;
    while(stiva[0]){

        tmp.clear();
        int nod=stiva[stiva[0]];

        if(!viz[nod]){

            dfs2(nod);
            rez.pb(tmp);
        }
        --stiva[0];

    }
    g<<rez.size()<<"\n";
    for(int i=0;i<rez.size();++i,g<<"\n")
        for(int j=0;j<rez[i].size();++j)
            g<<rez[i][j]<<" ";
    return 0;
}