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

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

const int NMAX = 1e5;

int N, M;
vector <int> g[NMAX + 5], r[NMAX + 5];

bool seen[NMAX + 5];
stack <int> st;

void dfs(int node) {
    seen[node] = true;

    for(int it : g[node]) {
        if(!seen[it]) {
            dfs(it);
        }
    }

    st.push(node);
}

vector <int> currentCtc;
vector <vector <int>> ctc;

void dfs2(int node) {
    currentCtc.push_back(node);
    seen[node] = false;

    for(int it : r[node]) {
        if(seen[it]) {
            dfs2(it);
        }
    }
}

int main() {
    cin >> N >> M;

    for(int i = 1; i <= M; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        r[y].push_back(x);
    }

    for(int i = 1; i <= N; i++) {
        if(!seen[i]) {
            dfs(i);
        }
    }

    while(!st.empty()) {
        int node = st.top();
        st.pop();

        if(seen[node]) {
            currentCtc.clear();
            dfs2(node);
            ctc.push_back(currentCtc);
        }
    }

    cout << (int)ctc.size() << '\n';
    for(vector <int> comp : ctc) {
        for(int node : comp) {
            cout << node << ' ';
        }
        cout << '\n';
    }

    return 0;
}