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


using namespace std;

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

int n, m;
vector<int> v[100005], idx, lowlink, in_stack;
vector<vector<int>> C; // SCC storage
stack<int> S;
int indecs = 0;

void tarjan(int x)
{
    idx[x] = lowlink[x] = ++indecs;
    S.push(x);
    in_stack[x] = 1;

    for (auto y: v[x])
    {
        if (idx[y] == 0)
        {
            tarjan(y);
            lowlink[x] = min(lowlink[x], lowlink[y]);
        }
        else if (in_stack[y])
        {
            lowlink[x] = min(lowlink[x], idx[y]);
        }
    }

    if (idx[x] == lowlink[x])
    {
        vector<int> con;
        int node;
        do
        {
            node = S.top();
            S.pop();
            in_stack[node] = 0;
            con.push_back(node);
        } while (node != x);
        C.push_back(con);
    }
}

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

    // Read input graph (1-based indexing)
    for (int i = 0; i < m; ++i)
    {
        int x, y;
        cin >> x >> y;
        v[x].push_back(y);
    }

    // Initialize arrays
    idx.resize(n + 1, 0);
    lowlink.resize(n + 1);
    in_stack.resize(n + 1, 0);

    // Run Tarjan's algorithm
    for (int i = 1; i <= n; ++i)
    {
        if (!idx[i])
        {
            tarjan(i);
        }
    }

    for(int i = 0; i < C.size(); ++i)
    {
        reverse(C[i].begin(), C[i].end());
    }
    // Print SCCs
    cout << C.size() << "\n";
    for (int i = 0; i < C.size(); ++i)
    {
        for (int j = 0; j < C[i].size(); ++j)
        {
            cout << C[i][j] << ' ';
        }
        cout << '\n';
    }

    return 0;
}