#include <bits/stdc++.h>
#define pb push_back
using namespace std;

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

const int NMAX=100000;

int N,M,nrc;

vector<int> G[NMAX+1],GT[NMAX+1],CTC[NMAX+1],stiva;

bool vis[NMAX+1];

void citire()
{
    int x,y;
    fin>>N>>M;
    for(int i=1;i<=M;++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int nod)
{
    vis[nod]=1;
    for(auto &x : G[nod])
    {
        if(vis[x]==0)
            dfs(x);
    }
    stiva.pb(nod);
}

void dfsGT(int nod)
{
    vis[nod]=0;
    CTC[nrc].pb(nod);
    for(auto &x : GT[nod])
    {
        if(vis[x]==1)
            dfsGT(x);
    }
}

void componente()
{
    for(int i=1;i<=N;++i)
    {
        if(vis[i]==0)
            dfs(i);
    }
    for(auto it= stiva.rbegin(); it!=stiva.rend();it++)
    {
        if(vis[*it]==1)
        {
            nrc++;
            dfsGT(*it);
        }
    }

}

void afis()
{
    fout<<nrc<<'\n';
    for(int i=1;i<=nrc;++i)
    {
        for(j=0;j<CTC[i].size();++j)
        {
            fout<<CTC[i][j]<<" ";
        }
        fout<<'\n';
    }
}

int main()
{
    citire();
    componente();
    afis();
    return 0;
}