#include <bits/stdc++.h>
using namespace std;

const int MAX = 100005;
vector<int> graph[MAX], tgraph[MAX];
vector<vector<int>> ans;
vector<int> tp, scc;
bitset<MAX> visited;

void dfs(int node)
{
    visited[node] = 1;
    for (int next : graph[node])
        if (!visited[next])
            dfs(next);

    tp.push_back(node);
}

void kosoraju(int node)
{
    visited[node] = 1;
    scc.push_back(node);

    for (int next : tgraph[node])
        if (!visited[next])
            kosoraju(next);
}

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

    for (int i = 1; i <= m; ++i)
    {
        int x, y;
        cin >> x >> y;
        graph[x].push_back(y);
        tgraph[y].push_back(x);
    }

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

    reverse(tp.begin(), tp.end());
    visited.reset();

    for (int i = 1; i <= n; ++i)
        if (!visited[i])
        {
            scc.clear();
            kosoraju(i);
            ans.push_back(scc);
        }

    cout << ans.size() << "\n";
    for (auto x : ans)
    {
        for (auto v : x)
            cout << v << " ";
        cout << "\n";
    }

    return 0;
}