#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>

#define NMAX 100005

using namespace std;

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

int n, m;
int x, y;
vector<int> l[NMAX];
int disc[NMAX], low[NMAX];
bool f[NMAX];
int timp;
stack<int> s;
int counter;
vector<int> ctc[NMAX];
int i, j;

void dfs(int);
bool comp(vector<int>, vector<int>);

int main()
{
    fin >>n>>m;
    for (i = 1; i <= m; ++i)
    {
        fin >>x>>y;
        l[x].push_back(y);
    }

    for (i = 1; i <= n; ++i)
        if (!f[i])
        {
            dfs(i);
        }

    sort(ctc+1, ctc+counter+1, comp);

    fout <<counter<<'\n';
    for (i = 1; i <= counter; ++i)
    {
        for (j = 0; j < ctc[i].size(); ++j)
            fout <<ctc[i][j]<<' ';
        fout <<'\n';
    }
    fout.close();
    return 0;
}

bool comp(vector<int> a, vector<int> b)
{
    return a[0] < b[0];
}

void dfs(int vf)
{
    int i; int vfnou;
    disc[vf] = ++timp; low[vf] = disc[vf];
    f[vf] = 1; s.push(vf);

    for (i = 0; i < l[vf].size(); ++i)
    {
        vfnou = l[vf][i];
        if (!f[vfnou])
        {
            dfs(vfnou);
            low[vf] = min(low[vf], low[vfnou]);
        }
        else
            low[vf] = min(low[vf], disc[vfnou]);
    }

    if (disc[vf] == low[vf])
    {
        counter ++;
        while (s.top() != vf)
        {
            ctc[counter].push_back(s.top());
            s.pop();
        }
        ctc[counter].push_back(s.top());
        s.pop();
        sort(ctc[counter].begin(), ctc[counter].end());
    }
}