#include <fstream>
#include <vector>
#include <stack>
#include <set>
using namespace std;
fstream cin("ctc.in", ios::in), cout("ctc.out", ios::out);
vector<vector<int>> v, vt;
vector<set<int>> sol;
vector<int> f;
stack<int> s;
int n, m, componente;
void dfs(int nod)
{
    f[nod] = 1;
    for (int next_nod : v[nod])
    {
        if (!f[next_nod])
        {
            dfs(next_nod);
        }
    }
    s.push(nod);
}
void dfst(int nod)
{
    f[nod] = 2;
    sol[componente - 1].insert(nod);
    for (int next_nod : vt[nod])
    {
        if (f[next_nod] == 1)
        {
            dfst(next_nod);
        }
    }
}
void kosaraju()
{
    f.resize(n + 1, 0);
    for (int i = 1; i <= n; i++)
    {
        if (!f[i])
        {
            dfs(i);
        }
    }
    for (; s.size(); s.pop())
    {
        if (f[s.top()] == 1)
        {
            componente++;
            sol.push_back(set<int>());
            dfst(s.top());
        }
    }
    cout << componente << '\n';
    for (auto componenta : sol)
    {
        for(auto x : componenta)
        {
            cout<<x<<' ';
        }
        cout<<'\n';
    }
}
int main()
{
    cin >> n >> m;
    v.resize(n + 1);
    vt.resize(n + 1);
    for (; m; m--)
    {
        int x, y;
        cin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    kosaraju();
    return 0;
}