#include <fstream>
#include <iostream>
#include <vector>
#include <stack>
#include <bitset>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define NMAX 100005
vector<int> g[NMAX], ng[NMAX];
vector<int> cmp[NMAX];
bitset<NMAX> viz, viz2;
stack<int> s;
void dfs(int x)
{
    viz[x] = 1;
    for (auto i : g[x])
    {
        if (viz[i] == 0)
        {
            dfs(i);
        }
    }
    s.push(x);
}
int ind = 0;
void dfs2(int x)
{

    viz2[x] = 1;
    for (auto i : ng[x])
    {
        if (viz2[i] == 0)
        {
            dfs2(i);
        }
    }
    cmp[ind].push_back(x);
}
int main()
{
    int n, m;
    fin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int a, b;
        fin >> a >> b;
        g[a].push_back(b);
        ng[b].push_back(a);
    }
    for (int i = 1; i <= n; i++)
    {
        if (viz[i] == 0)
            dfs(i);
    }
    while (!s.empty())
    {

        if (!viz2[s.top()])
        {
            dfs2(s.top());
            ind++;
        }
        s.pop();
    }
    fout << ind << '\n';
    for (int i = 0; i < ind; i++)
    {
        for (auto j : cmp[i])
        {
            fout << j << " ";
        }
        fout << '\n';
    }
    return 0;
}