#include <bits/stdc++.h>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int N(1e5 + 5);
int n, m, cnt;
bitset<N> viz;
stack<int> st;
vector<int> g[N], gt[N], ctc[N];
inline void DFS(int const& x) {
    viz[x] = 1;
    for (int const& y : g[x])
        if (!viz[y])
            DFS(y);
    st.emplace(x);
}
inline void DFSR(int const& x) {
    viz[x] = 1;
    ctc[cnt].emplace_back(x);
    for (int const& y : gt[x])
        if (!viz[y])
            DFSR(y);
}
void Kosaraju() {
    while (!st.empty()) {
        int x = st.top();
        st.pop();
        if (!viz[x]) {
            ++cnt;
            DFSR(x);
        }
    }
}
main() {
    fin >> n >> m;
    while (m--) {
        int x, y;
        fin >> x >> y;
        g[x].emplace_back(y);
        gt[y].emplace_back(x);
    }
    for (int i = 1; i <= n; ++i)
        if (!viz[i])
            DFS(i);
    viz.reset();
    Kosaraju();
    fout << cnt << '\n';
    for (int c = 1; c <= cnt; ++c, fout << '\n')
        for (int const& x : ctc[c])
            fout << x << ' ';
    return 0;
}