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

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

const int Nmax = 1e5;

vector<vector<int>>g, gt;
bool vis[Nmax];

void dfs(int nod, vector<vector<int>>& graf, vector<int>& addto)
{
    vis[nod] = 1;
    for(auto it: graf[nod])
        if(vis[it] == 0)
            dfs(it, graf, addto);
    addto.push_back(nod);
}

int main()
{
    int n, m, i, a, b;
    cin >> n >> m;
    g.resize(n + 5);
    gt.resize(n + 5);
    for(i = 1; i <= m; i ++)
    {
        cin >> a >> b;
        g[a].push_back(b);
        gt[b].push_back(a);
    }

    vector<int> st;
    for(i = 1; i <= n; i ++)
        if(vis[i] == 0)
          dfs(i, g, st);

    vector<vector<int>>ctc;
    for(i = 0; i <= n; i ++)
        vis[i] = 0;
    for(i = st.size() - 1; i >= 0; i --)
        if(vis[st[i]] == 0)
        {
            ctc.push_back(vector<int>());
            dfs(st[i], gt, ctc.back());
        }

    cout << ctc.size() << '\n';
    for(auto i: ctc)
    {
        for(auto j: i)
            cout << j << " ";
        cout << '\n';
    }
    return 0;
}