// prob1.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <fstream>
#include <vector>
#include <set>
#include <stack>
#include<cstring>
#define ll long long
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector<int>G[100005], GT[100005];
//stack<int>S;
vector<int>s;
vector<int>v;
set<int>rev[100005];
int nrc;
void dfs(int x)
{
    v[x] = 1;
    for (auto& i : G[x])
        if (v[i] == 0)
            dfs(i);
    s.push_back(x);
}
void dfsT(int x)
{
    rev[nrc].insert(x);
    v[x] = 1;
    for (auto& i : GT[x])
        if (v[i] == 0)
            dfsT(i);
}


int main()
{
    int n, m; cin >> n >> m;
    v = s = vector<int>(n + 1, 0);
    for (int i = 0; i < m; i++)
    {
        int x, y; cin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
        if (v[i] == 0)
            dfs(i);

    v = vector<int>(n + 1, 0);

    for (auto i = s.rbegin(); i != s.rend(); i++)
        if (v[*i] == 0)
        {
            nrc++;
            dfsT(*i);
        }

    cout << nrc-1 << '\n';
    for (int i = 1; i < nrc; i++, cout << '\n')
        for (auto& j : rev[i])cout << j << " ";

    return 0;
}