#include <bits/stdc++.h>

using namespace std;
const int N = 1e5;
vector <int> g[N + 5], g_t[N + 5];
bool vis[N + 5];
vector <int> traversal;
vector <vector <int>> cc;
void dfs(int u, bool transpose = false) {
    vis[u] = true;
    for(int v : transpose ? g_t[u] : g[u]) if(!vis[v])
        dfs(v, transpose);
    (transpose ? cc.back() : traversal).push_back(u);
}

int main()
{
    #ifndef HOME
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    #endif // HOME
    int n, m, u, v;
    cin >> n >> m;
    for(int i = 1; i <= m; i++)
        cin >> u >> v,
        g[u].push_back(v),
        g_t[v].push_back(u);
    for(int i = 1; i <= n; i++) if(!vis[i])
        dfs(i);
    fill(vis + 1, vis + n + 1, false);
    reverse(traversal.begin(), traversal.end());
    for(int u : traversal) if(!vis[u]) {
        cc.push_back({});
        dfs(u, true);
    }
    cout << cc.size() << "\n";
    for(auto& comp : cc) {
        for(int x : comp)
            cout << x << " ";
        cout << "\n";
    }
    return 0;
}