#include <vector>
#include <algorithm>
#include <string>
#include <string.h>
#include <cstring>
#include <queue>
#include <map>
#include <set>
#include <unordered_map>
#include <time.h>
#include <iomanip>
#include <deque>
#include <math.h>
#include <cmath>
#include <assert.h>
#include <stack>
#include <bitset>
#include <random>
#include <chrono>
#include <assert.h>
#include <fstream>



using namespace std;
using ll = long long;


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



const int maxn = 100005;

vector <int> gr[maxn], gr2[maxn];

int used[maxn];

vector <int> ord, comp;
vector <vector <int>> ans;



void dfs1(int nod){
    used[nod] = 1;

    for (auto& x : gr[nod]){
        if (!used[x]) dfs1(x);
    }
    ord.push_back(nod);
}

void dfs2 (int nod){
    used[nod] = 1;
    comp.push_back(nod);

    for (auto & x : gr2[nod]){
        if (!used[x]) dfs2(x);
    }
}



int main() {

    int n, m; cin >> n >> m;

    for (int i = 1; i <= m; i++){
        int a, b; cin >> a >> b;

        gr[a].push_back(b);
        gr2[b].push_back(a);
    }

    for (int i = 1; i <= n; i++){
        if (!used[i]) dfs1(i);
    }

    for (int i = 1; i <= n; i++) used[i] = 0;

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

    for (auto & i : ord){
        if (!used[i]) dfs2(i);
        if (!comp.empty()) ans.push_back(comp);
        comp.clear();
    }

    cout << ans.size() << '\n';
    for (auto& vec : ans){
        for (auto& elem : vec){
            cout << elem << ' ';
        }
        cout << '\n';
    }

    return 0;
}