#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

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

const int maxN = 100005;

int cnt;
bool visit[maxN];
vector <int> g[maxN];
vector <int> gT[maxN];
vector <int> compC[maxN];
vector <int> sTop;

void dfs(int node) {
    visit[node] = true;

    for(auto to : g[node])
        if(visit[to] == false)
            dfs(to);

    sTop.push_back(node);
}

void dfs2(int node) {
    visit[node] = true;
    compC[cnt].push_back(node);

    for(auto to : gT[node])
        if(visit[to] == false)
            dfs2(to);
}


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

    for(int i = 1; i <= m; ++i) {
        int u, v; fin >> u >> v;
        g[u].push_back(v);
        gT[v].push_back(u);
    }

    for(int i = 1; i <= n; ++i)
        if(visit[i] == false)
            dfs(i);

    for(int i = 1; i <= n; ++i)
        visit[i] = false;

    vector <int> :: reverse_iterator it;
    for(it = sTop.rbegin(); it != sTop.rend(); it++)
        if(visit[*it] == false) {
            cnt++;
            dfs2(*it);
        }

    fout << cnt << "\n";
    for(int i = 1; i <= cnt; ++i, fout << '\n')
        for(int node : compC[i])
            fout << node << " ";


    return 0;
}