#include <fstream>
#include <vector>

std::ifstream fin ("ctc.in");
std::ofstream fout ("ctc.out");

int const nmax = 100000;
std::vector <int> adj1[nmax + 5];
std::vector <int> adj2[nmax + 5];
std::vector <int> list;
std::vector <std::vector <int>> ans;
bool viz[nmax + 5];
bool added[nmax + 5];

void dfs (int x) {
    viz[x] = true;
    int lim = adj1[x].size();
    for (int i = 0; i < lim; i++)
        if (!viz[adj1[x][i]])
            dfs (adj1[x][i]);
    list.push_back(x);
}

int cnt;
void build_ctc (int x) {
    added[x] = true;
    int lim = adj2[x].size();
    ans[cnt].push_back(x);
    for (int i = 0; i < lim; i++)
        if (!added[adj2[x][i]])
            build_ctc (adj2[x][i]);
}

int main() {
    int n, m;
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y; fin >> x >> y;
        adj1[x].push_back(y);
        adj2[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs (i);
    for (int i = n - 1; i >= 0; i--)
        if (!added[list[i]]) {
            ans.push_back({});
            build_ctc (list[i]);
            cnt++;
        }
    fout << cnt << "\n";
    for (int i = 0; i < cnt; i++, fout << "\n") {
        int lim = ans[i].size();
        for (int x = 0; x < lim; x++)
            fout << ans[i][x] << " ";
    }
    return 0;
}