#include <fstream>
#include <iostream>
#include <vector>
using namespace std;

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

typedef vector<int> VI;
#define foor(it,v) for(__typeof(v.begin())it=v.begin();it!=v.end();++it)

vector <VI> G,G_t;
vector<VI> CTC;
VI st,zero;
vector<bool> viz;
int n,m,x,y,i;

void dfs(int nod)
{
    viz[nod]=true;
    foor(it,G[nod]) if(!viz[*it]) dfs(*it);
    st.push_back(nod);
}

void dfs_t(int nod)
{
    viz[nod]=true;
    foor(it,G_t[nod]) if(!viz[*it]) dfs_t(*it);
    CTC.back().push_back(nod);
}

int main()
{
    f>>n>>m;
    G.resize(n+1);
    G_t.resize(n+1);
    viz.resize(n+1,0);
    for(;m;--m)
    {
        f>>x>>y;
        G[x].push_back(y);
        G_t[y].push_back(x);
    }

    for(i=1;i<=n;++i) if(!viz[i]) dfs(i);
    viz.assign(n+1,0);
    for(;st.size();st.pop_back()) if(!viz[st.back()])
    {
        CTC.resize(CTC.size()+1);
        dfs_t(st.back());
    }
    g<<CTC.size()<<'\n';
    foor(itc,CTC)
    {
        foor(it,(*itc)) g<<*it<<' ';
        g<<'\n';
    }
    return 0;
}