#include <bits/stdc++.h>

#define NMAX 100002

using namespace std;

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

int n, m, viz[NMAX], conex_components;
vector<int> G[NMAX];
vector<int> GT[NMAX];
vector<int> rez[NMAX];
stack<int> s;

void read_data()
{
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int nod)
{
    viz[nod] = 1;
    for (auto vec : G[nod])
        if (!viz[vec]) dfs(vec);

    s.push(nod);
}

void dfs_t(int nod)
{
    viz[nod] = 2;
    rez[conex_components].push_back(nod);

    for (auto vec : GT[nod])
        if (viz[vec] == 1) dfs_t(vec);
}

int main()
{
    read_data();

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

    while (!s.empty())
    {
        if (viz[s.top()] == 1)
        {
            conex_components++;
            dfs_t(s.top());
        }
        s.pop();
    }

    fout << conex_components << "\n";
    for (int i = 1; i <= conex_components; i++)
    {
        for (auto nod : rez[i])
            fout << nod << " ";
        fout << "\n";
    }

    return 0;
}