#include <fstream>
#include <algorithm>
#include <vector>
#include <cstring>
#include <stack>
#define NMAX 100005
using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

stack <int> st;
vector < int > Add[NMAX], ans[NMAX], Inv[NMAX];
bool vis[NMAX];
int N, M, K;

void DFSFirst(int node)
{
    vis[node] = true;
    for(int i = 0; i < Add[node].size(); i++){
        if(vis[Add[node][i]] == false){
            DFSFirst(Add[node][i]);
        }
    }
    st.push(node);
}

void DFSecond(int node){
    vis[node] = true;
    ans[K].push_back(node);
    //cout << "* ";
    for(int i = 0; i < Inv[node].size(); i++){
        if(vis[Inv[node][i]] == false){
            DFSecond(Inv[node][i]);
        }
    }
}

int main()
{
    int x, y;
    cin >> N >> M;
    for(int i = 1; i <= M; i++){
        cin >> x >> y;
        Add[x].push_back(y);
        Inv[y].push_back(x);
    }
    for(int i = 1; i <= N; i++){
        if(vis[i] == false){
            DFSFirst(i);
        }
    }
    memset(vis,false,sizeof(vis));
    while(!st.empty()){
        int v = st.top();
        st.pop();
        if(vis[v] == false){
            ++K;
            DFSecond(v);
        }
    }
    cout << K << "\n";
    for(int i = 1; i <= K; i++){
        for(int j = 0; j < ans[i].size(); j++){
            cout << ans[i][j] << " ";
        }
        cout << "\n";
    }
    return 0;
}