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

const int NMAX = 1e5;

vector <int> g[NMAX + 1];
int tin[NMAX + 1];
int low[NMAX + 1];
bool on[NMAX + 1];

stack <int> s;

vector <vector <int> > sol;


void compute_ctc(int nod)
{
    vector <int> vec;
    while (!s.empty() and s.top() != nod)
    {
        vec.push_back(s.top());
        on[s.top()] = 0;
        s.pop();
    }
    vec.push_back(nod);
    if (!s.empty())
        s.pop();
    on[nod] = 0;
    sol.push_back(vec);
}

void dfs(int nod, int parent)
{
    s.push(nod);
    on[nod] = 1;
    static int time = 0;
    tin[nod] = ++time;
    low[nod] = tin[nod];
    for (int x : g[nod])
        if (tin[x] == 0)
        {
            dfs(x, nod);
            low[nod] = min(low[nod], low[x]);
        }
        else if (on[x])
        {
            low[nod] = min(low[nod], tin[x]);
        }
    if (low[nod] == tin[nod])
        compute_ctc(nod);
}

signed main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int n, m, i;
    cin >> n >> m;
    for (i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
    }
    for (i = 1; i <= n; i++)
        if (tin[i] == 0)
            dfs(i, 0);
    cout << sol.size() << "\n";
    for (i = 0; i < sol.size(); i++, cout << "\n")
        for (int x : sol[i])
            cout << x << " ";
}