#include <fstream>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>

using namespace std;

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

int n, m;
vector<int> G[100010];
vector<int> GT[100010];
vector<int> stop;
vector<int> vis(100001);

void dfs(int nod) {
    vis[nod] = 1;
    for(auto nodnou : G[nod]) {
        if(!vis[nodnou]) {
            dfs(nodnou);
        }
    }
    stop.push_back(nod);
}

void dfs1(int nod, vector<int> & aux) {
    vis[nod] = 1;
    for(auto nodnou: GT[nod]) {
        if(!vis[nodnou]) {
            dfs1(nodnou, aux);
        }
    }
    aux.push_back(nod);
}

int main() {
    cin >> n >> m;
    for(int i = 1; i <= m; ++i) {
        int x, y; cin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

    for(int i = 1; i <= n; ++i) {
        if(!vis[i]) {
            dfs(i);
        }
    }
    reverse(stop.begin(), stop.end());
    
    vis = vector<int> (100001, 0);
    vector<vector<int>> ans;
    for(auto x : stop) {
        if(!vis[x]) {
            vector<int> aux;
            dfs1(x, aux);
            ans.push_back(aux);
        }
    }

    cout << ans.size() << '\n';
    for(auto v : ans) {
        for(auto x : v) {
            cout << x << ' ';
        }
        cout << '\n';
    }

    return 0;   
}