#include <fstream>
#include <vector>

using namespace std;

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

const int Max = 100010;

vector<int> g[Max],gt[Max];
vector<vector<int> > comp;
int q[Max],nr;
char vaz[Max];

void dfs1(int nod)
{
    vaz[nod] = 1;
    for(vector<int>::iterator it = g[nod].begin(); it != g[nod].end(); it++)
        if(!vaz[*it])
            dfs1(*it);

    q[++nr] = nod;
}

void dfs2(int nod,vector<int> &comp)
{
    vaz[nod] = 0;
    comp.push_back(nod);
    for(vector<int>::iterator it = gt[nod].begin(); it != gt[nod].end(); it++)
        if(vaz[*it])
            dfs2(*it,comp);
}

int main()
{
    int n,m,x,y;
    in >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        in >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    for(int i = 1; i <= n; i++)
        if(!vaz[i])
            dfs1(i);
    for(int i = nr; i; i--)
        if(vaz[q[i]])
        {
            comp.push_back(vector<int>());
            dfs2(q[i],comp.back());
        }
    out << comp.size() << "\n";

    for(int i = 0; i < comp.size(); i++)
    {
        for(int j = 0; j < comp[i].size(); j++)
            out << comp[i][j] << " ";
        out << "\n";
    }
    return 0;
}