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

using namespace std;

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

const int maxN = 100005;
int nrctc;
vector <int> G[maxN], Gback[maxN], comp[maxN], ordine;
bool used[maxN];

void dfs1(int nod){
    used[nod] = 1;
    for(int vecin : G[nod])
        if(!used[vecin])
            dfs1(vecin);
    ordine.push_back(nod);
}

void dfs2(int nod){
    used[nod] = 1;
    comp[nrctc].push_back(nod);
    for(int vecin : Gback[nod])
        if(!used[vecin])
            dfs2(vecin);
}

int main()
{
    int n, m;
    cin >> n >> m;
    for(int i = 1; i <= m; i++){
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
        Gback[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!used[i])
            dfs1(i);
    for(int i = 1; i <= n; i++)
        used[i] = 0;
    reverse(ordine.begin(), ordine.end());
    for(int elem : ordine){
        if(used[elem])
            continue;
        nrctc++;
        dfs2(elem);
    }
    cout << nrctc << '\n';
    for(int i = 1; i <= nrctc; i++){
        for(int elem : comp[i])
            cout << elem << ' ';
        cout << '\n';
    }
    return 0;
}