#include <bits/stdc++.h>

using namespace std;

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

int k, sir[100005], viz[100005], cc, n, m;

vector <int> G[100005];
vector <int> L[100005];
vector <int> s[100005];

void DFS1(int nod)
{
    viz[nod] = 1;

    for(auto i : L[nod])
        if(!viz[i])
            DFS1(i);

    sir[++k] = nod;
}

void DFS2(int nod)
{
    viz[nod] = 1;

    for(auto i : G[nod])
        if(!viz[i])
            DFS2(i);

    s[cc].push_back(nod);
}
void Citire()
{
    int x, y;

    fin >> n >> m;

    for(int i = 1; i <= m; i++)
    {
        fin >> x >> y;

        L[x].push_back(y);
        G[y].push_back(x);
    }

    for(int i = 1; i <= n; i++)
        if(!viz[i])
            DFS1(i);

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

    for(int i = k; i >= 1; i--)
        if(!viz[sir[i]]){
            ++cc;
            DFS2(sir[i]);
        }

    fout << cc << "\n";
    for(int i = 1; i <= cc; i++)
    {
        for(int j = 0; j < s[i].size(); j++)
            fout << s[i][j] << " ";
        fout << "\n";
    }
}
int main()
{
    Citire();
    return 0;
}