#include <bits/stdc++.h>

using namespace std;

int n, m;
vector<vector<int>> edges;
vector<vector<int>> scc;
int nrScc = -1, currentIndex = 0;
vector<int> lowlink;
vector<bool> onStack;
vector<int> idx;
stack<int> st;
vector<int> comp;

void read() {
    cin >> n >> m;
    edges.resize(n);
    for(int i=0; i<m; i++) {
        int u, v;
        cin >> u >> v;
        edges[u-1].push_back(v-1);
    }
}

void dfs(int v) {
    lowlink[v] = idx[v] = currentIndex++;
    onStack[v] = true;
    st.push(v);
    for(int u : edges[v]) {
        if(idx[u] == -1) {
            dfs(u);
            lowlink[v] = min(lowlink[v], lowlink[u]);
        } else if(onStack[u] == true)
            lowlink[v] = min(lowlink[v], idx[u]);
    }

    if(lowlink[v] == idx[v]) {
        comp.clear();
        int node;
        do {
            node = st.top();
            comp.push_back(node);
            onStack[node] = false;
            st.pop();
        } while(node!=v);
        scc.push_back(comp);
    }
}

void tarjan() {
    for(int i=0; i<(int)edges.size(); i++)
        if(idx[i] == -1)
            dfs(i);
}

void show() {
    for(int v=0; v<edges.size(); v++) {
        cout << v << " : ";
        for(int u: edges[v])
            cout << u << " ";
        cout << "\n";
    }
}

void showScc() {
    cout << scc.size() << " ";
    for(int i=0; i<scc.size(); i++) {
        for(int node: scc[i])
            cout << node + 1 << " ";
        cout << "\n";
    }
}

int main() {
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    read();
    idx.resize(n), lowlink.resize(n), onStack.resize(n);
    idx.assign(n, -1), onStack.assign(n, 0);
    //show();
    tarjan();
    showScc();
    return 0;
}