#include <bits/stdc++.h>
using namespace std;
 
ifstream in("ctc.in");
ofstream out("ctc.out");
 
 
const int N = 1e5;

struct graf
{
    vector<int> v;
}
la[N + 5];
 
stack<int> stk;
int id[N + 5], low[N + 5];
bool onStk[N + 5];
int nrCTC, nrid;
vector<vector<int>> ctc;

void dfs(int nod)
{
    low[nod] = id[nod] = ++nrid;
    stk.push(nod);
    onStk[nod] = 1;

    for (int i = 0; i < la[nod].v.size(); i++)
    {
        int to = la[nod].v[i];

        if (id[to] == -1) dfs(to);
        if (onStk[to]) low[nod] = min(low[to], low[nod]);
    }

    if (low[nod] == id[nod])
    {
        vector<int> aux;
        while (stk.top() != nod)
        {
            aux.push_back(stk.top());
            onStk[stk.top()] = 0;
            stk.pop();
        }
        aux.push_back(stk.top());
        onStk[stk.top()] = 0;
        stk.pop();
        ctc.push_back(aux);
        nrCTC++;
    }
}

void Tarjan(int n)
{
    for (int i = 1; i <= n; i++) id[i] = -1;

    for (int i = 1; i <= n; i++)
        if (id[i] == -1)
        {
            dfs(i);
        }
}

int main()
{
    int n, m; in>> n >> m;

    for (int i = 1; i <= m; i++)
    {
        int x, y; in>> x >> y;
        la[x].v.push_back(y);
    }

    Tarjan(n);
    out<< nrCTC << '\n';
    for (int i = 0; i < ctc.size(); i++)
    {
        for (int j = 0; j < ctc[i].size(); j++)
        out<< ctc[i][j] << ' ';
        out<< '\n';
    }
    return 0;
}