#include <fstream>
#include <vector>
#include <stack>
#include <iostream>

#define UNDEFINED  -1
const int NMAX = 1e5 + 1;

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

std :: vector <int> graf[NMAX];
std :: vector <std :: vector <int> > sol;
int n, m;

void tarjanAlg();

void DFS(int i, std :: vector <int> & disc, std :: vector <int>& low, std :: stack <int> & stk
        , std :: vector <bool> & inStack);


int main() {



    f >> n >> m;
    for (int i = 0; i < m; i++ ){
        int a, b;
        f >> a >> b;
        graf[a - 1].push_back(b - 1);
    }

    tarjanAlg();

    g << sol.size() << "\n";
    for (auto linie : sol ) {
        for (auto elem : linie) {
            g << elem << " ";
        }
        g << "\n";
    }


    return 0;
}

void tarjanAlg(){

    std :: vector <int> disc(n + 1,-1); // discovery_time
    std :: vector <int> low(n + 1, -1);
    std :: vector <bool> inStack(n,false);
    std :: stack <int> stk;

    for (int i = 0; i < n; i++)
        if (disc[i] == UNDEFINED)
            DFS(i,disc,low,stk,inStack);
}

void DFS(int u, std :: vector <int> & disc, std :: vector <int>& low, std :: stack <int> & stk
        , std :: vector <bool> & inStack){

    static int time = 0;
    disc[u] = low[u] = time;

    time += 1;

    stk.push(u);
    inStack[u] = true;

    for (int v : graf[u]){
        if (disc[v] == UNDEFINED){
            DFS(v, disc, low, stk, inStack );
            low[u] = std :: min (low[u], low[v]);
        }
        else
        if (inStack[u])
            low[u] = std :: min (low[u], disc[v]);
    }
    std :: vector <int> aux;

    if (disc[u] == low[u]){
        while (stk.top() != u){
            aux.push_back(stk.top()+1);
            //g << stk.top() + 1 << "  ";
            inStack[stk.top()] = false;
            stk.pop();
        }
        aux.push_back(stk.top()+1);
        //g << stk.top() + 1 << "\n";
        sol.push_back(aux);
        inStack[u] = false;
        stk.pop();
    }

}