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

ifstream f("ctc.in");
ofstream g("ctc.out");

const int NMAX = 1e5+5;
vector<int> graf[NMAX], grafT[NMAX], sol[NMAX];
int n, m, cnt;
vector<int> postorder;
bool vis[NMAX], visT[NMAX];

void dfs(int nod) {
    vis[nod] = 1;
    for(int i = 0; i < (int)graf[nod].size(); i++) {
        int next = graf[nod][i];
        if(!vis[next]) {
            dfs(next);
        }
    }
    postorder.push_back(nod);
}

void dfsT(int nod) {
    visT[nod] = 1;
    sol[cnt].push_back(nod);
    for(int i = 0; i < (int)grafT[nod].size(); i++) {
        int next = grafT[nod][i];
        if(!visT[next]) {
            dfsT(next);
        }
    }
}

int main()
{
    f >> n >> m;
    while(m--) {
        int x, y;
        f >> x >> y;
        graf[x].push_back(y);
        grafT[y].push_back(x);
    }
    for(int i = 1; i <= n; i++) {
        if(!vis[i]) {
            dfs(i);
        }
    }
    for(int i = postorder.size() - 1; i >= 0; i--) {
        if(!visT[postorder[i]]) {
            cnt++;
            dfsT(postorder[i]);
        }
    }
    g << cnt << '\n';
    for(int i = 1; i <= cnt; i++) {
        for(int j = 0; j < (int)sol[i].size(); j++) {
            g << sol[i][j] << ' ';
        }
        g << '\n';
    }
    return 0;
}