#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>

using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

#define NMAX 100005

int n, m, x, y, rez;
vector<int>G[NMAX], GT[NMAX], S, sol[NMAX];

int viz[NMAX];

void dfs(int nod)
{
    viz[nod]=1;
    for (auto &vecin: G[nod])
        if(!viz[vecin])
        dfs(vecin);
    S.push_back(nod);
}

void dfsGT(int nod)
{
    sol[rez].push_back(nod);
    viz[nod]=1;
    for(auto &vecin: GT[nod])
        if(!viz[vecin])
            dfsGT(vecin);
}

int main()
{
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    memset(viz, 0, sizeof(viz));
    for(int i=S.size()-1; i>=0; i--)
    {
        if(!viz[S[i]]){
            rez++;
            dfsGT(S[i]);
        }
    }
    fout<<rez<<"\n";
    for(int i=1; i<=rez; i++){
        for(int j=0; j<sol[i].size(); j++)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    return 0;
}