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

const int maxim = 100002;
int n, m, parcurse[maxim];
vector<int> a[maxim], transpus[maxim], pluss, minuss;
vector<vector<int>> solutie;
vector<int> ctcActual;

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

void citireOrientat(){
    int x, y;
    in >> n >> m;
    for(int i = 1; i <= m; i++){
        in >> x >> y;
        a[x].push_back(y);
        transpus[y].push_back(x); //formez graful transpus
    }
}

bool apartine(vector<int> v, int x) {
    for(auto i: v)
        if(i == x)
            return 1;
    return 0;
}

void dfs(int x){
    pluss.push_back(x);
    for(auto j: a[x])
        if(apartine(pluss, j) == 0)
            dfs(j);
}

void dfsTranspus(int x){
    minuss.push_back(x);
    if(apartine(pluss, x)){
        parcurse[x] = 1;
        ctcActual.push_back(x);
    }
    for(auto j: transpus[x])
        if(apartine(minuss, j) == 0)
            dfsTranspus(j);
}


int main(){
    citireOrientat();
    for(int i = 1; i <= n; i++){
        if(parcurse[i] == 0){
            dfs(i);
            dfsTranspus(i);
            if(ctcActual.empty() == 0)
                solutie.push_back(ctcActual);
            ctcActual.clear();
            minuss.clear();
            pluss.clear();
        }
    }
    out << solutie.size() << '\n';
    for(auto i: solutie){
        for(auto j: i)
            out << j << " ";
        out << '\n';
    }
    return 0;
}