#include <bits/stdc++.h>
#define NMAX 100001

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

int n, m, d[NMAX], low[NMAX], step;

vector <int> v[NMAX];
vector < vector <int> > ans;
bool check[NMAX];
stack <int> st;

void DFS(int nod)
{
    if(d[nod])    return;
    d[nod] = low[nod] = ++step;
    st.push(nod);
    check[nod] = true;

    for(int i = 0; i < v[nod].size(); i++)
    {
        int nod_urm = v[nod][i];

        if(d[nod_urm] == 0)
        {
            DFS(nod_urm);
            low[nod] = min(low[nod], low[nod_urm]);
        }
        else
            if(check[nod_urm])
            {
                low[nod] = min(low[nod], d[nod_urm]);

            }




    }
    if(low[nod] == d[nod])
    {
        vector <int> p;
            while(!st.empty() && st.top()!= nod)
            {
                p.push_back(st.top());
                check[st.top()] = false;
                st.pop();
            }

            st.pop();

            check[nod] = false;
            p.push_back(nod);
            ans.push_back(p);
    }
}
int main()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int a, b;
        fin >> a >> b;
        v[a].push_back(b);
    }
    for(int i = 1; i <= n; i++)
        DFS(i);

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