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

using namespace std;

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

int n, m, nrc;
bool viz[100008], viz2[100008];
vector <int> cc[100008], g[100008], gt[100008];
stack <int> s;

void dfs(int nod)
{
    viz[nod] = true;

    for(auto it = g[nod].begin(); it != g[nod].end(); ++it)
    {
        if(!viz[*it])
        {
            dfs(*it);
        }
    }

    s.push(nod);
}
void dfs2(int nod, int ccc)
{
    cc[ccc].push_back(nod);
    viz2[nod] = true;

    for(auto it = gt[nod].begin(); it != gt[nod].end(); ++it)
    {
        if(!viz2[*it])
        {
            dfs2(*it, ccc);
        }
    }
}

int main()
{
    cin >> n >> m;

    for(int i = 1; i <= m; ++i)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        gt[b].push_back(a);
    }

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

    while(!s.empty())
    {
        int i = s.top();
        s.pop();

        if(!viz2[i])
            dfs2(i, ++nrc);
    }

    cout << nrc << '\n';

    for(int i = 1; i <= nrc; ++i)
    {
        for(auto it = cc[i].begin(); it != cc[i].end(); ++it)
        {
            cout << *it << ' ';
        }

        cout << '\n';
    }

    return 0;
}