#include <bits/stdc++.h>
#define Nmax 100005
using namespace std;

int n, m, cnt, viz1[Nmax], viz2[Nmax];
ifstream f("ctc.in");
ofstream g("ctc.out");

vector <int> G[Nmax], GT[Nmax], ans[Nmax], v;

void read()
{
    f >> n >> m;

    int x, y;
    for (int i = 1; i <= m; ++i) {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs1(int node)
{
    viz1[node] = 1;
    for (int i = 0; i < G[node].size(); ++i)
        if (!viz1[G[node][i]])
            dfs1(G[node][i]);
    v.push_back(node);
}

void dfs2(int node)
{
    viz2[node] = cnt;
    ans[cnt].push_back(node);
    for (int i = 0; i < GT[node].size(); ++i)
        if (!viz2[GT[node][i]])
            dfs2(GT[node][i]);
}

void solve()
{
    for (int i = 1; i <= n; ++i)
        if (!viz1[i])
            dfs1(i);

    for (vector <int>::reverse_iterator it = v.rbegin(); it != v.rend(); it++)
        if (!viz2[*it]) {
            ++cnt;
            dfs2(*it);
        }
}

void show()
{
    g << cnt << "\n";
    for (int i = 1; i <= cnt; ++i) {
        for (int j = 0; j < ans[i].size(); ++j)
            g << ans[i][j] << " ";
        g << "\n";
    }
}

int main()
{
    read();
    solve();
    show();
    return 0;
}