#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], g[N], componente[N];
stack<int> S;

int p[N], m[N] , nr_componente;

void dfs(int nod)
{
    p[nod] = 1;
    for(auto &i : v[nod])
    {
        if(p[i] == 0)
            dfs(i);
    }
    S.push(nod);
}

void dfs_transpus(int nod)
{
    p[nod] = 1;
    componente[nr_componente].push_back(nod);
    for(auto &i : g[nod])
    {
        if(p[i] == 0)
            dfs_transpus(i);
    }

}

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);
        g[b].push_back(a);
    }
    for(int i=1; i<=n; i++)
        if(p[i] == 0)
            dfs(i);
    for(int i=1; i<=n; i++)
        p[i] = 0;
    while(!S.empty())
    {
        int nod = S.top();
        S.pop();
        if(p[nod] == 0)
        {
            nr_componente++;
            dfs_transpus(nod);
        }
    }
    cout << nr_componente << '\n';
    for(int i=1;i<=nr_componente;i++)
    {
        for(auto j : componente[i])
            cout << j << ' ';
        cout << '\n';
    }
}