#include <bits/stdc++.h>

using namespace std;
#define int long long int
#define pb push_back
#define sz(x) (int)(x.size())
#define all(a) a.begin(), a.end()
#define nl '\n'
const int N = 3e5 + 5, INF = 1e9, mod = 998244353;

int n, m, ctc, used[N];
vector<int> g[N], gt[N], scc[N];
stack<int> stk;

void dfs1(int node) {
    used[node] = 1;
    for (auto it : g[node]) {
        if (!used[it]) {
            dfs1(it);
        }
    }
    stk.push(node);
}

void dfs2(int node) {
    used[node] = 1;
    scc[ctc].pb(node);
    for (auto it : gt[node]) {
        if (!used[it]) {
            dfs2(it);
        }
    }
}

void run_case(int test_case) {
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
        gt[v].pb(u);
    }
    for (int i = 1; i <= n; i++) {
        if (!used[i]) {
            dfs1(i);
        }
    }
    for (int i = 1; i <= n; i++) {
        used[i] = 0;
    }
    while (!stk.empty()) {
        int node = stk.top();
        stk.pop();
        if (!used[node]) {
            ++ctc;
            dfs2(node);
        }
    }
    cout << ctc << '\n';
    for (int i = 1; i <= ctc; i++) {
        for (auto it : scc[i]) {
            cout << it << ' ';
        }
        cout << '\n';
    }
};

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int T = 1;
    ///cin >> T;
    for (int t = 1; t <= T; ++t) {
#ifdef _DEBUG
        cerr << "=== Subtask " << t << " ===" << '\n';
#endif
        run_case(t);
#ifdef _DEBUG
        cerr << nl;
#endif
    }
}