#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, i, a, b;
int vaz[100005];
vector<int> ad[100005], ad2[100005], v;
vector<vector<int>> sol;

void topoSort(int nod){
    vaz[nod]=1;
    for(auto vecin: ad[nod]){
        if(!vaz[vecin])
            topoSort(vecin);
    }
    v.push_back(nod);
}

void dfs(int nod){
    vaz[nod]=1;
    sol[sol.size()-1].push_back(nod);
    for(int vecin: ad2[nod]){
        if(!vaz[vecin])
            dfs(vecin);
    }
}

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

    for(i=1;i<=m;i++){
        fin>>a>>b;
        ad[a].push_back(b);
        ad2[b].push_back(a);
    }

    for(i=1;i<=n;i++){
        if(!vaz[i])
            topoSort(i);
    }

    for(i=1;i<=n;i++){
        vaz[i]=0;
    }

    for(i=v.size()-1;i>=0;i--){
        int nod=v[i];
        if(!vaz[nod]){
            sol.push_back(vector<int> {});
            dfs(nod);
        }
    }

    fout<<sol.size()<<'\n';
    for(i=0;i<sol.size();i++){
        for(auto nod: sol[i]){
            fout<<nod<<" ";
        }
        fout<<'\n';
    }


    return 0;
}