#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

#define cin in
#define cout out

const int N = 2e5 + 1;

vector<int> v[N];
vector<vector<int>> componente2;
stack<int> S;
int low[N], index[N], noduri , nr_componente;
bool in_stiva[N];



void dfs(int nod)
{
    index[nod] = ++noduri;
    low[nod] = index[nod];
    S.push(nod);
    in_stiva[nod] = 1;
    for(auto &i : v[nod])
    {
        if(index[i] == 0)
        {
            dfs(i);
            low[nod] = min(low[i],low[nod]);
        }
        else
        {
            if(in_stiva[i] != 0)
                low[nod] = min(index[i], low[nod]);
        }
    }
    vector<int> c1;
    if(index[nod] == low[nod])
    {
        while(!S.empty())
        {
            int varf = S.top();
            S.pop();
            in_stiva[varf] = 0;
            c1.push_back(varf);
            if(varf == nod)
                break;
        }
        componente2.push_back(c1);
        nr_componente++;
    }
}

signed main()
{
    int n, M;
    cin >> n >> M;
    for (int i = 1, a, b; i <= M; i++)
    {
        cin >> a >> b;
        v[a].push_back(b);
    }
    for(int i=1; i<=n; i++)
    {
        if(index[i] == 0)
            dfs(i);
    }
    cout << nr_componente << '\n';
    for(auto i : componente2){
        for(auto j : i)
            cout << j << ' ';
        cout << '\n';
    }

}