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

int n, m;
vector<int> g[100001], gt[100001];
stack<int> nodes;
bool vis[100001];

void dfs(int node) {
    vis[node] = 1;
    for (int i = 0; i < g[node].size(); ++i) {
        if (!vis[g[node][i]]) {
            dfs(g[node][i]);
        }
    }
    nodes.push(node);
}

vector<int> ans[100001];
int ctc;

void dfst(int node) {
    vis[node] = 1;
    ans[ctc].push_back(node);
    for (int i = 0; i < gt[node].size(); ++i) {
        if (!vis[gt[node][i]]) {
            dfst(gt[node][i]);
        }
    }
}

int main()  {
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    cin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for (int i = 1; i <= n; ++i) {
        if (!vis[i]) {
            dfs(i);
        }
    }
    memset(vis, 0, sizeof(vis));
    while (!nodes.empty()) {
        if (!vis[nodes.top()]) {
            ++ctc;
            dfst(nodes.top());
        }
        nodes.pop();
    }
    cout << ctc << "\n";
    for (int i = 1; i <= ctc; ++i) {
        for (auto i : ans[i]) {
            cout << i << " ";
        }
        cout << "\n";
    }
}