#include <fstream>
#include <vector>
#include <bitset>

using namespace std;

const int N = 100001;

vector <int> a_s[N], a_p[N];
vector <vector<int>> ctc;
bitset <N> viz;
int n, m, sol[N], nrs, cc[N];

void dfs(int x)
{
    viz[x] = 1;
    for (auto y: a_s[x])
    {
        if (!viz[y])
        {
            dfs(y);
        }
    }
    sol[++nrs] = x;
}

void dfs_p(int x)
{
    viz[x] = 1;
    cc[x] = ctc.size() - 1;
    for (auto y: a_p[x])
    {
        if (!viz[y])
        {
            dfs_p(y);
        }
    }
}

int main()
{
    ifstream in("ctc.in");
    ofstream out("ctc.out");
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x, y;
        in >> x >> y;
        a_s[x].push_back(y);
        a_p[y].push_back(x);
    }
    in.close();
    for (int i = 1; i <= n; i++)
    {
        if (!viz[i])
        {
            dfs(i);
        }
    }
    viz.reset();
    for (int i = nrs; i >= 1; i--)
    {
        if (!viz[sol[i]])
        {
            vector <int> v;
            ctc.push_back(v);
            dfs_p(sol[i]);
        }
    }
    out << ctc.size() << "\n";
    for (int i = 1; i <= n; i++)
    {
        ctc[cc[i]].push_back(i);
    }
    for (auto comp: ctc)
    {
        for (auto x: comp)
        {
            out << x << " ";
        }
        out << "\n";
    }
    out.close();
    return 0;
}