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

using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector <vector<int>> v, vrev, scc;
vector <int> kosaraju;
const int NMAX = 100005;
int vis[NMAX], visrev[NMAX];
void dfs(int u)
{
    vis[u] = 1;
    for(auto it: v[u])
        if(!vis[it])
            dfs(it);
    kosaraju.push_back(u);
}
void dfsrev(int u)
{
    scc.back().push_back(u);
    visrev[u] = 1;
    for(auto it: vrev[u])
        if(!visrev[it])
            dfsrev(it);
}
void Kosaraju(int n)
{
    int i;
    for(i = 1; i <= n; i++)
        if(!vis[i])
            dfs(i);

    reverse(kosaraju.begin(), kosaraju.end());

    for(auto it: kosaraju)
    {
        if(!visrev[it])
        {
            scc.push_back({});
            dfsrev(it);
        }
    }
}
int main()
{
    int n, m, i, a, b;
    cin >> n >> m;
    v.resize(n + 1);
    vrev.resize(n + 1);
    for(i = 1; i <= m; i++)
    {
        cin >> a >> b;
        v[a].push_back(b);
        vrev[b].push_back(a);
    }
    Kosaraju(n);
    cout << scc.size() << '\n';
    for(i = 0; i < scc.size(); i++)
    {
        for(auto it: scc[i])
            cout << it << ' ';
        cout << '\n';
    }
    return 0;
}