#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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

vector<int> List[100001];
vector<int> ReverseList[100001];
vector<int> SCC[100001];
int NoSCC;
int visited[100001];
stack<int>stiva;

void DFS(int node){
    visited[node]=1;
    for(int i=0;i<List[node].size();i++){
        if(visited[List[node][i]]==0)
            DFS(List[node][i]);
    }
    stiva.push(node);
}

void ReverseDFS(int node){
    visited[node]=2;
    SCC[NoSCC].push_back(node);
    for(int i=0;i<ReverseList[node].size();i++){
        if(visited[ReverseList[node][i]]==1)
            ReverseDFS(ReverseList[node][i]);
    }
}

int main() {
    int n,x,y,m,i;
    fin>>n>>m;
    for(i=1;i<=m;i++){
        fin>>x>>y;
        List[x].push_back(y);
        ReverseList[y].push_back(x);
    }

    for(i=1;i<=n;i++){
        if(visited[i]==0)
            DFS(i);
    }

    while(!stiva.empty()){
        if(visited[stiva.top()]==1){
            NoSCC++;
            ReverseDFS(stiva.top());
        }
        stiva.pop();
    }

    fout<<NoSCC<<endl;

    for(int j=1;j<=NoSCC;j++){
        sort(SCC[j].begin(),SCC[j].end());
        for(i=0;i<SCC[j].size();i++)
            fout<<SCC[j][i]<<" ";
        fout<<endl;
    }

    return 0;
}