#include <bits/stdc++.h>
using namespace std;

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

vector<int> v[100001], tc[100001];
stack<int> stiva;
bool inStiva[100001];
int n, ctc, id, viz[100001], leg[100001];

void citire()
{
    int m;
    f>>n>>m;
    for(int i = 1; i <= m; i++)
    {
        int x, y;
        f>>x>>y;
        v[x].push_back(y);
    }
}

void dfs(int nod)
{
    stiva.push(nod);
    inStiva[nod] = 1;
    viz[nod] = leg[nod] = ++id;
    for(int i = 0; i < v[nod].size(); i++)
    {
        if(!viz[v[nod][i]])
        {
            dfs(v[nod][i]);
            leg[nod] = min(leg[nod], leg[v  [nod][i]]);
        }
        else if(inStiva[v[nod][i]])
            leg[nod] = min(leg[nod], leg[v[nod][i]]);
    }
    if(leg[nod] == viz[nod])
    {
        ctc++;
        while(true)
        {
            tc[ctc].push_back(stiva.top());
            inStiva[stiva.top()] = 0;
            if(stiva.top() == nod)
            {
                stiva.pop();
                break;
            }
            stiva.pop();
        }
    }
}

int main()
{
    citire();
    for(int i = 1; i <= n; i++)
        if(!viz[i])
            dfs(i);
    g<<ctc<<'\n';
    for(int i = 1; i <= ctc; i++){
        for(int j = 0; j < tc[i].size(); j++)
            g<<tc[i][j]<<' ';
        g<<'\n';
    }
    return 0;
}