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

using namespace std;

const int N = 100000 + 7;
int n, m;
vector<int> g[N], ig[N];
int ord[N], top = 0;
bool u[N];
int what[N];
vector<int> sol[N];

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

void idfs(int a, int cur)
{
    sol[cur].push_back(a);
    what[a] = cur;
    u[a] = 1;
    for (auto &b : ig[a])
    {
        if (u[b] == 0)
        {
            u[b] = 1;
            idfs(b, cur);
        }
    }
}

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

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

}