#include <fstream>
#include <string.h>
#include <vector>


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


int viz[100001];
int st[100001];

vector <int> G[100001];
vector <int> gt[100001];
vector <int> ctc[100001];

int sol=0;

void dfs(int nod)
{
    viz[nod]=1;
    for(int i = 0; i < G[nod].size(); i++)
            if(!viz[G[nod][i]])
                dfs(G[nod][i]);

    st[++st[0]]=nod;
}

void dfstrans(int nod)
{
    viz[nod] = 1;
    for(int i = 0 ; i < gt[nod].size(); i++)
            if(!viz[gt[nod][i]]) dfstrans(gt[nod][i]);

    ctc[sol].push_back(nod);
}

int main()
{
    int n, m, x, y;

    f >> n >> m;

    for(int i = 1; i <= m; i++)
    {
            f >> x >> y;
            G[x].push_back(y);
            gt[y].push_back(x);
    }

    for(int i = 0; i <= sizeof(st)/sizeof(st[0]); i++)
        st[i] = 0;

    for(int i = 0; i <= sizeof(viz)/sizeof(viz[0]); i++)
        viz[i] = 0;

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

    for(int i = 0; i <= sizeof(viz)/sizeof(viz[0]); i++)
        viz[i] = 0;

    for(int i = n; i>0 ; i--)
            if(!viz[st[i]])
    {
            sol++;
            dfstrans(st[i]);
    }

    g << sol<< '\n';
    for(int i=1; i <= sol; i++)
    {
            for(int j=0; j < ctc[i].size(); j++)
                    g << ctc[i][j]<<" ";
            g << "\n";
    }

    return 0;
}