#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n, m, viz1[100001], viz2[100001], cnt;

vector <int> a[100001], b[100001], ans[100001];

stack <int> stiva;

void dfs1(int nod)
{
    viz1[nod] = 1;

    for (auto it : a[nod]) {
        if (!viz1[it]) {
            dfs1(it);
        }
    }

    stiva.push(nod);
}

void dfs2(int nod)
{
    viz2[nod] = 1;

    for (auto it : b[nod]) {
        if (!viz2[it]) {
            dfs2(it);
        }
    }

    ans[cnt].push_back(nod);
}

int main()
{
    f >> n >> m;

    while (m--) {
        int x, y;

        f >> x >> y;

        a[x].push_back(y);
        b[y].push_back(x);
    }

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

    while (!stiva.empty()) {
        int nod = stiva.top();

        stiva.pop();

        if (!viz2[nod]) {
            cnt++;
            dfs2(nod);
        }
    }

    g << cnt << '\n';

    for (int i = 1; i <= cnt; ++i) {
        for (auto it : ans[i]) {
            g << it << ' ';
        }

        g << '\n';
    }

    return 0;
}