#include <bits/stdc++.h>

using namespace std;
const int N = 1e5 + 1, M = 2e5 + 1;

int n, m, x, y;
bool vis[N];
vector<vector<int>> ctc;
vector<int> invmc[N], mc[N], topsort;

void dfs(int nod)
{
    vis[nod] = 1;

    for (auto i : mc[nod])
    {
        if (!vis[i])
            dfs(i);
    }

    topsort.push_back(nod);
}

void kos(int nod)
{
    vis[nod] = 0;
    ctc.back().push_back(nod);
    for (auto i : invmc[nod])
    {
        if (vis[i])
            kos(i);
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> n >> m;
    for (int i = 1; i <= m; ++i)
    {
        cin >> x >> y;
        mc[x].push_back(y);
        invmc[y].push_back(x);
    }

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

    reverse(topsort.begin(), topsort.end());
    vector<int> aux;

    for (auto i : topsort)
    {
        if (vis[i])
        {
            ctc.push_back(aux);
            kos(i);
        }
    }

    cout << ctc.size() << '\n';
    for (auto i : ctc)
    {
        for (auto j : i)
            cout << j << ' ';
        cout << '\n';
    }

    return 0;
}