#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <stack>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int NMAX = 1e5 + 5;
vector<int> g[NMAX], gt[NMAX], res[NMAX];
bool vis[NMAX];
stack<int> st;

void dfs1(int curr) {
    vis[curr] = true;
    for (auto nod : g[curr]) {
        if (!vis[nod])
            dfs1(nod);
    }
    st.push(curr);
}

void dfs2(int curr, const int &ind) {
    res[ind].push_back(curr);
    vis[curr] = true;
    for (auto nod : gt[curr]) {
        if (!vis[nod])
            dfs2(nod, ind);
    }
}

int main() {

    int n, m;
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;

        g[x].push_back(y);
        gt[y].push_back(x);
    }

    for (int i = 1; i <= n; i++) {
        if (!vis[i])
            dfs1(i);
    }

    memset(vis, 0, sizeof(vis));
    int k = 0;
    while (!st.empty()) {
        int nod = st.top();
        st.pop();

        if (!vis[nod]) {
            dfs2(nod, ++k);
        }
    }

    fout << k << '\n';
    for (int i = 1; i <= k; i++) {
        for (auto x : res[i]) {
            fout << x << ' ';
        }
        fout << '\n';
    }


    return 0;
}