#include <fstream>
#include <vector>
#include <bitset>

using namespace std;
const int NMAX = 100002;

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

bitset <NMAX> f;
void dfs(int start, vector <vector<int>>& edges, vector <int>& add_to) {
    f[start] = 1;
    for(auto node : edges[start]) {
        if(!f[node])
            dfs(node, edges, add_to);
    }
    add_to.push_back(start);
}
int n;
vector <vector <int>> v, inv;
vector <vector <int>> ctc;
vector <int> st;
int main()
{
    int m, a, b;
    cin >> n >> m;
    v.resize(n + 1);
    inv.resize(n + 1);
    for(int i = 1; i <= m; i++) {
        cin >> a >> b;
        v[a].push_back(b);
        inv[b].push_back(a);
    }
    for(int i = 1; i <= n; i++) {
        if(!f[i])
            dfs(i, v, st);
    }
    f = 0;
    for(int i = st.size() - 1; i >= 0; i--) {
        if(!f[st[i]]) {
            ctc.push_back(vector<int>());
            dfs(st[i], inv, ctc.back());
        }
    }
    cout << ctc.size() << '\n';
    for(int i = 0; i < ctc.size(); i++) {
        for(auto node : ctc[i])
            cout << node << " ";
        cout << '\n';
    }
    return 0;
}