#include <iostream>
#include <cstdio>
#include <vector>

using namespace std;

const int N = 100000 + 7;
int n, m;
vector<int> g[N], sol[N];
bool u[N];
int ord[N], top, ans[N];

void dfs(int i)
{
    u[i] = 1;
    for (auto &j : g[i])
    {
        if (u[j] == 0)
        {
            dfs(j);
        }
    }
    ord[++top] = i;
}

void d2s(int i, int cur)
{
    u[i] = 1;
    ans[i] = cur;
    for (auto &j : g[i])
    {
        if (u[j] == 0)
        {
            d2s(j, cur);
        }
    }
}

int main()
{
    freopen ("ctc.in", "r", stdin);
    freopen ("ctc.out", "w", stdout);

//    freopen ("hacker.in", "r", stdin);

    cin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
    }
    for (int i = 1; i <= n; i++)
    {
        if (u[i] == 0)
        {
            dfs(i);
        }
    }
    for (int i = 1; i <= n; i++)
    {
        u[i] = 0;
    }
    int cur = 0;
    for (int i = 1; i <= n; i++)
    {
        if (u[ord[i]] == 0)
        {
            cur++;
            d2s(ord[i], cur);
        }
    }
    cout << cur << "\n";
    for (int i = 1; i <= n; i++)
    {
        sol[ans[i]].push_back(i);
    }
    for (int i = 1; i <= cur; i++)
    {
        for (auto &j : sol[i])
        {
            cout << j << " ";
        }
        cout << "\n";
    }

}